U.S. patent number 10,333,100 [Application Number 15/506,593] was granted by the patent office on 2019-06-25 for organic electroluminescent device.
This patent grant is currently assigned to SUMITOMO CHEMICAL COMPANY, LIMITED. The grantee listed for this patent is SUMITOMO CHEMICAL COMPANY, LIMITED. Invention is credited to Shinichi Morishima, Masato Shakutsui.
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United States Patent |
10,333,100 |
Morishima , et al. |
June 25, 2019 |
Organic electroluminescent device
Abstract
An organic electroluminescent device comprising: a transparent
support substrate having flexibility; a light emitting element
disposed on the transparent support substrate and including a pair
of electrodes and a luminescent layer disposed between the pair of
electrodes; a sealing material layer disposed on the transparent
support substrate so as to cover and seal the light emitting
element; and a sealing substrate disposed on the sealing material
layer, wherein based on an arithmetic average of roughness profile
defined in JIS B 0601-1994, the surface roughness of a surface of
the sealing substrate beside the sealing material layer has a
smaller value than the surface roughness of the other surface of
the sealing substrate, and the arithmetic average of roughness
profile of the surface of the sealing substrate beside the sealing
material layer and a thickness of the sealing material layer
satisfy a requirement represented by the following formula (I):
0.002<(Ra/t)<0.2 (I) [in the formula (I), Ra denotes the
arithmetic average of roughness profile of JIS B 0601-1994 of the
surface of the sealing substrate beside the sealing material layer,
and t denotes the thickness of the sealing material layer].
Inventors: |
Morishima; Shinichi (Niihama,
JP), Shakutsui; Masato (Niihama, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
SUMITOMO CHEMICAL COMPANY, LIMITED |
Tokyo |
N/A |
JP |
|
|
Assignee: |
SUMITOMO CHEMICAL COMPANY,
LIMITED (Tokyo, JP)
|
Family
ID: |
55399762 |
Appl.
No.: |
15/506,593 |
Filed: |
August 26, 2015 |
PCT
Filed: |
August 26, 2015 |
PCT No.: |
PCT/JP2015/074077 |
371(c)(1),(2),(4) Date: |
February 24, 2017 |
PCT
Pub. No.: |
WO2016/031877 |
PCT
Pub. Date: |
March 03, 2016 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20170256737 A1 |
Sep 7, 2017 |
|
Foreign Application Priority Data
|
|
|
|
|
Aug 29, 2014 [JP] |
|
|
2014-175615 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05B
33/04 (20130101); H01L 51/5246 (20130101); H01L
51/5243 (20130101); H05B 33/02 (20130101); H01L
51/5253 (20130101); H01L 51/0097 (20130101); H01L
51/56 (20130101); H01L 2251/5338 (20130101); H01L
2251/558 (20130101); Y02E 10/549 (20130101) |
Current International
Class: |
H01L
51/52 (20060101); H05B 33/02 (20060101); H01L
51/00 (20060101); H05B 33/04 (20060101); H01L
51/56 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2004-171806 |
|
Jun 2004 |
|
JP |
|
2006-185643 |
|
Jul 2006 |
|
JP |
|
2008-010211 |
|
Jan 2008 |
|
JP |
|
2010-198980 |
|
Sep 2010 |
|
JP |
|
2010-231977 |
|
Oct 2010 |
|
JP |
|
2011-222334 |
|
Nov 2011 |
|
JP |
|
2012-212675 |
|
Nov 2012 |
|
JP |
|
2013095991 |
|
May 2013 |
|
JP |
|
2011/114860 |
|
Sep 2011 |
|
WO |
|
2016031876 |
|
Mar 2016 |
|
WO |
|
Other References
Machine English Translation of JP 2004-171806, Nakamura, published
Jun. 17, 2004. cited by examiner .
Machine English Translation of JP 2010-231977, Takarazumi et al.,
published Oct. 14, 2010. cited by examiner .
Surface Roughness (JISB B 0601-2001) [online], [retrieved on Sep.
19, 2018], retrieved from "http://www.engineering.com". cited by
examiner .
International Search Report of PCT/JP2015/074077 dated Nov. 10,
2015. cited by applicant .
International Preliminary Report on Patentability and Translation
of Written Opinion, dated Mar. 9, 2017, from the International
Bureau in counterpart International application No.
PCT/JP2015/074077. cited by applicant .
Communication dated Mar. 27, 2018 from the European Patent Office
in counterpart Application No. 15835305.2. cited by applicant .
Junji Miyake, "Overview of Copper Foil," Japan Institute of
Electronic Imaging; vol. 6, No. 6 (2003), pp. 528-533. cited by
applicant.
|
Primary Examiner: Gumedzoe; Peniel M
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
The invention claimed is:
1. An organic electroluminescent device comprising: a transparent
support substrate having flexibility; a light emitting element
disposed on the transparent support substrate and including a pair
of electrodes and a luminescent layer disposed between the pair of
electrodes; a sealing material layer disposed on the transparent
support substrate so as to cover and seal the light emitting
element; and a sealing substrate disposed on the sealing material
layer, wherein based on an arithmetic average of roughness profile
defined in JIS B 0601-1994, the surface roughness of a surface of
the sealing substrate beside the sealing material layer has a
smaller value than the surface roughness of an opposite surface of
the sealing substrate, and the arithmetic average of roughness
profile of the surface of the sealing substrate beside the sealing
material layer and a thickness of the sealing material layer
satisfy a requirement represented by the following formula (I):
0.002<(Ra/t).ltoreq.0.03 (I) [in the formula (I), Ra denotes the
arithmetic average of roughness profile of JIS B 0601-1994 of the
surface of the sealing substrate beside the sealing material layer,
and t denotes the thickness of the sealing material layer].
2. The organic electroluminescent device according to claim 1,
wherein the arithmetic average of roughness profile of the surface
of the sealing substrate beside the sealing material layer is 0.1
to 1.0 .mu.m.
3. The organic electroluminescent device according to claim 1,
wherein the thickness of the sealing material layer is 5 to 120
.mu.m.
4. The organic electroluminescent device according to claim 1,
wherein the sealing substrate is made of any of metal materials of
copper, copper alloys, aluminum, and aluminum alloys.
5. The organic electroluminescent device according to claim 1,
wherein the sealing substrate is made of an electrolytic copper
foil.
6. The organic electroluminescent device according to claim 1,
wherein the arithmetic average of roughness profile Ra of the
opposite surface, of the sealing substrate is 0.25 to 3.8
.mu.m.
7. The organic electroluminescent device according to claim 1,
wherein (Ra/t).ltoreq.0.01.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a National Stage of International Application
No. PCT/JP2015/074077 filed Aug. 26, 2015, claiming priority based
on Japanese Patent Application No. 2014-175615 filed Aug. 29, 2014,
the contents of all of which are incorporated herein by reference
in their entirety.
TECHNICAL FIELD
The present invention relates to an organic electroluminescent
device.
BACKGROUND ART
An organic electroluminescent device deteriorates due to the
permeation of an oxygen gas, water vapor, or the like to the inside
of the device, and lowers the light-emission performance due to the
generation of an emission-defective spot called a dark spot. Hence,
for the purpose of inhibiting an oxygen gas or water vapor from
permeating the inside of a device, use of a sealing material has
been proposed in the field of the organic electroluminescent
device. For example, International Publication No. WO2011/114860
(Patent Literature 1) discloses an organic electroluminescent
device in which at least a transparent anode layer, an organic
layer including a luminescent layer, and a cathode layer are
layered in this order on a transparent base material, the organic
electroluminescent device including a first sealing film disposed
on the transparent anode layer side, a second sealing film disposed
on the cathode layer side, and a sealing layer made of a
thermosetting resin and provided on the surface of the cathode
layer opposite to the organic layer. However, the conventional
organic electroluminescent device as described in Patent Literature
1 is not necessarily satisfactory from the viewpoint of preventing
the occurrence of a short circuit after being bent.
CITATION LIST
Patent Literature
[PLT 1] International Publication No. WO2011/114860
SUMMARY OF INVENTION
Technical Problem
The present invention has been made in view of the foregoing
problems of the conventional technique, and has an object to
provide an organic electroluminescent device capable of
satisfactorily inhibiting the occurrence of a short circuit after
being bent.
Solution to Problem
In order to achieve the above object, the present inventors have
earnestly studied and consequently found that an organic
electroluminescent device (OLED: simply referred to as an "organic
EL device" in some cases below) is made capable of satisfactorily
inhibiting the occurrence of a short circuit after being bent, when
the organic EL device comprises: a transparent support substrate
having flexibility; a light emitting element disposed on the
transparent support substrate and including a pair of electrodes
and a luminescent layer disposed between the pair of electrodes; a
sealing material layer disposed on the transparent support
substrate so as to cover and seal the light emitting element; and a
sealing substrate disposed on the sealing material layer, wherein
based on an arithmetic average of roughness profile defined in JIS
B 0601-1994, the surface roughness of a surface of the sealing
substrate beside the sealing material layer has a smaller value
than the surface roughness of the other surface of the sealing
substrate, and the arithmetic average of roughness profile of the
surface of the sealing substrate beside the sealing material layer
and a thickness of the sealing material layer satisfy a requirement
represented by the following formula (I): 0.002<(Ra/t)<0.2
(I) [in the formula (I), Ra denotes the arithmetic average of
roughness profile of JIS B 0601-1994 of the surface of the sealing
substrate beside the sealing material layer, and t denotes the
thickness of the sealing material layer]. Thus, the present
inventors have completed the present invention.
Specifically, an organic electroluminescent device according to the
present invention comprises:
a transparent support substrate having flexibility;
a light emitting element disposed on the transparent support
substrate and including a pair of electrodes and a luminescent
layer disposed between the pair of electrodes;
a sealing material layer disposed on the transparent support
substrate so as to cover and seal the light emitting element;
and
a sealing substrate disposed on the sealing material layer,
wherein
based on an arithmetic average of roughness profile defined in JIS
B 0601-1994, the surface roughness of a surface of the sealing
substrate beside the sealing material layer has a smaller value
than the surface roughness of the other surface of the sealing
substrate, and
the arithmetic average of roughness profile of the surface of the
sealing substrate beside the sealing material layer and a thickness
of the sealing material layer satisfy a requirement represented by
the following formula (I): 0.002<(Ra/t)<0.2 (I) [in the
formula (I), Ra denotes the arithmetic average of roughness profile
of JIS B 0601-1994 of the surface of the sealing substrate beside
the sealing material layer, and t denotes the thickness of the
sealing material layer].
In the above organic electroluminescent device of the present
invention, the arithmetic average of roughness profile of the
surface of the sealing substrate beside the sealing material layer
(Ra) is preferably 0.1 to 1.0 .mu.m.
In addition, in the above organic electroluminescent device of the
present invention, the thickness of the sealing material layer is
preferably 5 to 120 .mu.m.
Further, in the above organic electroluminescent device of the
present invention, the sealing substrate is preferably made of any
of metal materials of copper, copper alloys, aluminum, and aluminum
alloys, and is more preferably made of a copper foil produced by an
electrolytic process.
Advantageous Effects of Invention
According to the present invention, it is possible to provide an
organic electroluminescent device capable of satisfactorily
inhibiting the occurrence of a short circuit after being bent.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic vertical cross-sectional view schematically
illustrating a preferred embodiment of an organic
electroluminescent device in the present invention.
FIG. 2 is a schematic vertical cross-sectional view schematically
illustrating one embodiment of a gas-barrier multilayer film
suitably usable as a transparent support substrate included in the
organic electroluminescent device of the present invention.
FIG. 3 is a schematic upper side view schematically illustrating a
structure of an organic electroluminescent device obtained in
Example 1 when viewed from a sealing substrate side.
DESCRIPTION OF EMBODIMENTS
Hereinafter, preferred embodiments of the present invention will be
described in details with reference to the drawings. In the
following description and the drawings, the same or equivalent
elements will be assigned with the same sign, and redundant
explanation thereof will be omitted.
An organic electroluminescent device of the present invention
comprises:
a transparent support substrate having flexibility;
a light emitting element disposed on the transparent support
substrate and including a pair of electrodes and a luminescent
layer disposed between the pair of electrodes;
a sealing material layer disposed on the transparent support
substrate so as to cover and seal the light emitting element;
and
a sealing substrate disposed on the sealing material layer,
wherein
based on an arithmetic average of roughness profile defined in JIS
B 0601-1994, the surface roughness of a surface of the sealing
substrate beside the sealing material layer has a smaller value
than the surface roughness of the other surface of the sealing
substrate, and
the arithmetic average of roughness profile of the surface of the
sealing substrate beside the sealing material layer and a thickness
of the sealing material layer satisfy a requirement represented by
the following formula (I): 0.002<(Ra/t)<0.2 (I) [in the
formula (I), Ra denotes the arithmetic average of roughness profile
of JIS B 0601-1994 of the surface of the sealing substrate beside
the sealing material layer, and t denotes the thickness of the
sealing material layer].
FIG. 1 is a schematic vertical cross-sectional view schematically
illustrating a preferred embodiment of an organic
electroluminescent device in the present invention. The organic
electroluminescent device in the embodiment illustrated in FIG. 1
includes a transparent support substrate 1, alight emitting element
2, a sealing material layer 3, and a sealing substrate 4. These
components will be described one by one below.
[Transparent Support Substrate 1]
The transparent support substrate 1 illustrated in FIG. 1 has
flexibility (bendability). As for the "flexibility" mentioned
herein, the transparent support substrate 1 may just have
bendability required for a substrate for a general flexible organic
EL device, and a material thereof is not particularly limited.
However, it is preferable that the transparent support substrate 1
be a thin film glass from the viewpoint of gas barrier properties
or be a plastic base material from the viewpoints of weight
reduction and fracture resistance. In addition, the transparent
support substrate 1 is not particularly limited but may be any
substrate having light transmittance (transparency) to the extent
that the substrate can be utilized as a substrate on the light
extraction side of an organic EL device. Thus, any publicly-known
transparent substrate usable as a substrate on the light extraction
side of an organic EL device can be used as needed, and a substrate
having transparency with a total light transmittance of 80% or more
can be preferably used.
Even when a plastic is used as a base material, the transparent
support substrate 1 preferably has gas barrier properties. As the
transparent support substrate 1, a publicly-known gas barrier film
usable as a flexible transparent substrate of an organic EL device
can be used as needed. For example, a gas-barrier multilayer film
described in Japanese Unexamined Patent Application Publication No.
2011-73430 (JP 2011-73430 A) can be preferably used (in particular,
a multilayer body in which two or more of such films are bonded
together with an adhesive is more preferable).
Moreover, as the transparent support substrate 1, the following
gas-barrier multilayer film is preferable the film can achieve
higher water vapor permeation prevention performance; the
gas-barrier multilayer film includes first and second thin film
layers having gas barrier properties, first and second base
material layers, and an adhesive layer, and has a multilayer
structure in which the first thin film layer, the first base
material layer, the adhesive layer, the second thin film layer, and
the second base material layer are layered in this order. This is
because. Here, if such a gas-barrier multilayer film is used, it is
preferable that one of the electrodes of the light emitting element
be stacked on the first thin film layer of the gas-barrier
multilayer film from the viewpoint of more highly preventing
deterioration of the organic EL device due to water vapor and the
like. Hereinafter, the gas-barrier multilayer film suitably usable
as such a transparent support substrate 1 according to the present
invention will be described with reference to FIG. 2.
A gas-barrier multilayer film in an embodiment illustrated in FIG.
2 is a gas-barrier multilayer film including a first base material
layer 100(a), a second base material layer 100(b), and a first thin
film layer 101(a) having gas barrier properties, a second thin film
layer 101(b) having gas barrier properties, and an adhesive layer
102, and having a multilayer structure in which the first thin film
layer 101(a), the first base material layer 100(a), the adhesive
layer 102, the second thin film layer 101(b), and the second base
material layer 100(b) are layered in this order.
As described above, the gas-barrier multilayer film includes two
base material layers called the first base material layer 100(a)
and the second base material layer 100(b). Here, in the case where
the number of such base material layers is only one (in the case of
a structure in which the gas-barrier multilayer film does not
include any one of the first base material layer and the second
base material layer), it tends to be so difficult to inhibit
deterioration of the organic EL device at a sufficiently high level
that the deterioration proceeds at faster speed and the storage
life becomes shorter than in the case where the number of base
material layers is two or more. For example, assume that the second
base material layer 100(b) is not present in the embodiment
illustrated in FIG. 2. In this case, even if a thin film layer
having gas barrier properties is formed on the first base material
layer and then a step of drying the first base material is further
carried out, the surface of the first base material opposite to the
thin film layer having gas barrier properties is exposed to the
outside, and a time until a moisture content in the first base
material reaches a saturated content tends to increase
significantly due to permeation of moisture into the first base
material from the surface exposed to the outside. Therefore, even
if the drying step is carried out during the production, the effect
of drying tends to fail to be fully utilized. On the other hand,
consider a case where the first base material layer 100(a) is not
present. If second and third thin film layers are formed on both
sides of the second base material and a step of drying the second
base material layer is also carried out after the thin film layers
are formed, it is difficult to remove moisture inside the second
base material because both sides of the base material are covered
by the thin film layers that exhibit barrier properties. As a
result, the effect of drying tends to fail to be fully
utilized.
Base materials for forming the base material layer 100(a) and the
base material layer 100(b) may be the same as or different from
each other. Any publicly-known base material usable to form a
gas-barrier multilayer film can be used as needed. As for such base
materials, it is preferable that at least one of the first base
material layer 100(a) and the second base material layer 100(b) be
made of an organic polymer material from the viewpoints of
flexibility, light transmittance, and flatness of base materials,
and weight reduction of a device. Moreover, it is more preferable
that both the first base material layer 100(a) and the second base
material layer 100(b) be made of an organic polymer material(s)
because it is possible to obtain higher flexibility (bendability)
and improve workability in processing such as parting and bending
processing of the base material.
As such organic polymer materials, polyester-based resins such as
polyethylene terephthalate (PET) and polyethylene naphthalate
(PEN); polyolefin-based resins such as polyethylene (PE),
polypropylene (PP), and cyclic polyolefin; polyamide-based resins;
polycarbonate-based resins; polystyrene-based resins; polyvinyl
alcohol-based resins; saponified copolymers of ethylene-vinyl
acetate copolymers; polyacrylonitrile-based resins; acetal-based
resins; polyimide-based resins; and the like are preferably usable
because they can be used as a colorless and transparent base
material.
In addition, as such an organic polymer material, preferred is a
polymer material comprising a polymer containing heteroatoms
(oxygen, nitrogen, etc.) other than carbon and hydrogen. A polymer
material (polyolefin or the like) comprising a hydrocarbon polymer
composed only of carbon and hydrogen is of a nonpolar polymer in
which almost no polarization occurs in molecules, and thus
generally has difficulty in exhibiting sufficient hydrophilicity.
In contrast, a polymer material comprising a polymer containing
heteroatoms (oxygen, nitrogen, etc.) is more likely to cause
polarization stemming from their heteroatoms, and generally has
sufficiently high hydrophilicity. Here, a highly hydrophilic
polymer material can achieve a high moisture content under a use
environment (usually under conditions at room temperature (about
25.degree. C.) and normal humidity), and thus can be made to have
hygroscopicity efficiently by drying to sufficiently remove the
internal moisture. For this reason, in the case where such a
polymer material comprising a polymer containing heteroatoms other
than carbon and hydrogen is used as a material for a base material,
a gas-barrier multilayer film having a higher hygroscopicity can be
produced more efficiently, and the gas-barrier multilayer film thus
produced can exhibit higher water vapor permeation prevention
performance when used as a substrate for an organic EL device.
Here, a preferable heteroatom in such a polymer containing
heteroatoms other than carbon and hydrogen is an oxygen atom
because such a base material, when used in a gas-barrier multilayer
film, enables the film to exhibit a high hygroscopicity.
As such an organic polymer material, polyesters having ester bonds
are preferable from the following viewpoints. Specifically, a
colorless and transparent base material can be obtained. Moreover,
the polyester is a polymer containing heteroatoms other than
hydrogen and therefore is capable of exhibiting a high
hygroscopicity when used after drying or the like, so that the
polyester can impart higher water vapor permeation prevention
performance to the transparent support substrate 1. Among the
polyesters, it is particularly preferable to use a polyester having
a benzene ring (for example, PET (polyethylene terephthalate) or
PEN (polyethylene naphthalate)) from the viewpoints that the base
material can be enhanced in the transparency and the workability in
film formation, and can be further improved also in the strength
and the heat resistance.
In addition, the thickness of such a base material is not
particularly limited. In the case of forming a thin film layer
directly on a surface of the base material, however, it is
preferable to set the thickness appropriate for film deposition
depending on a kind of the thin film layer to be formed thereon.
For example, the thickness of the base material is preferably 5 to
500 .mu.m, because the base material with such a thickness can be
conveyed in vacuum in the process of forming a thin film layer on a
surface of the base material and thus the thin film can be formed
on the surface of the base material under vacuum conditions.
Moreover, the thickness of the base material is more preferably 50
to 200 .mu.m and most preferably 50 to 100 .mu.m from the viewpoint
that, in the case of forming the thin film layer by using a plasma
CVD method, such a thickness allows use of a method of forming the
thin film layer by performing electric discharge through the base
material.
Further, the thickness of the base material has the following
nature. Specifically, for example, in a case where members in each
of which a thin film layer is formed on a base material are bonded
together to produce a gas-barrier multilayer film, the bonding step
is not particularly affected by the thickness of the base material.
Thus, regardless of the method of producing the gas-barrier
multilayer film, a base material with any thickness can be used
without particular limitation, if the thickness allows a thin film
layer to be deposited. In other words, the thickness of the base
material may be designed as appropriate as long as the thickness
allows a thin film layer to be formed on a surface of the base
material, and enables the base material to satisfactorily support
the thin film layer.
Meanwhile, the gas-barrier multilayer film in the embodiment
illustrated in FIG. 2 includes two thin film layers called the
first thin film layer 101(a) and the second thin film layer 101(b).
Here, in the case where the number of such thin film layers is only
one (in the case of a structure in which the gas-barrier multilayer
film does not include any one of the first thin film layer and the
second thin film layer), it tends to be so difficult to inhibit
deterioration of the organic EL device at a sufficiently high level
that the deterioration proceeds at faster speed and the storage
life becomes shorter than in the case where the number of thin film
layers is two or more. For example, assume that only the first thin
film layer 101(a) is present in the embodiment illustrated in FIG.
2. In this case, even if the gas-barrier multilayer film is
produced through a step of drying the first base material, the
absence of a barrier layer on the surface of the gas-barrier
multilayer film opposite to the surface covered with the first thin
film layer having gas barrier properties tends to facilitate
permeation of moisture into the first base material from the
surface opposite to the surface covered with the first thin film
layer having gas barrier properties, and a time until the moisture
content in the base material reaches a saturated moisture content
tends to be significantly shortened. Therefore, even if the drying
step is carried out during the production, the effect of drying
tends to fail to be fully utilized. Also, in the case where only
the second thin film layer is present in the embodiment illustrated
in FIG. 2, an organic EL is formed directly on the first base
material, and the moisture inside the base material tends to
directly deteriorate the organic EL.
Moreover, both the first thin film layer 101(a) and the second thin
film layer 101(b) need to be layers formed of thin films having gas
barrier properties (thin film layers). The "gas barrier properties"
mentioned herein may be properties that satisfy at least one of the
following requirements (A) to (C):
[Requirement (A)]
as a result of comparison of a "gas-transmission rate of base
material (unit: mol/m.sup.2sP)" and a "gas-transmission rate of
base material with thin film layer formed (unit: mol/m.sup.2sP)"
measured by a method in accordance with JIS K 7126 (issued in
2006), the "gas-transmission rate of base material with thin film
layer formed" takes a value smaller by two or more digits than (a
value of 1/100 or less of) a value of the "gas-transmission rate of
base material";
[Requirement (B)]
as a result of comparison of a "water vapor permeability of base
material (unit: g/m.sup.2sP)" and a "water vapor permeability of
base material with thin film layer formed (unit: g/m.sup.2sP)"
measured by a method in accordance with JIS K 7129 (issued in
2008), the "water vapor permeability of the base material with thin
film layer formed" takes a value smaller by two or more digits than
(a value of 1/100 or less of) a value of the "water vapor
permeability of base material"; and
[Requirement (C)]
as a result of comparison of a "water vapor permeability of the
base material (unit: g/m.sup.2sP)" and a "water vapor permeability
of base material with thin film layer formed (unit: g/m.sup.2sP)"
measured by a method in accordance with a method described in
Japanese Unexamined Patent Application Publication No. 2005-283561
(JP 2005-283561 A), the "water vapor permeability of base material
with thin film layer formed" takes a value smaller by two or more
digits than (a value of 1/100 or less of) a value of the "water
vapor permeability of base material". Note that the water vapor
permeability of a base material with a thin film layer having water
vapor barrier properties (gas barrier properties) formed thereon
generally has a value of 10.sup.-2 g/m.sup.2/day or less. For this
reason, when the above requirements (B) and (C) are examined, the
"water vapor permeability of base material with thin film layer
formed" preferably has a value of 10.sup.-2 g/m.sup.2/day or less.
Moreover, it is more preferable that such a thin film layer having
gas barrier properties satisfy the above requirement (C).
Moreover, such a thin film layer having gas barrier properties has
a thickness preferably in a range of 5 to 3000 nm, more preferably
in a range of 10 to 2000 nm, and most preferably in a range of 100
to 1000 nm. When the thickness of the thin film layer is smaller
than the above lower limit, the thin film layer tends to have poor
gas barrier properties such as oxygen gas barrier properties and
water vapor barrier properties. On the other hand, when the
thickness of the thin film layer is larger than the above upper
limit, the thin film layer tends to easily degrade the gas barrier
properties due to bending.
As for a kind of each of the first and second thin film layers
having gas barrier properties, any publicly-known thin films having
gas barrier properties may be used as needed without particular
limitation. Each of these thin film layers is preferably a thin
film layer containing at least one of metal oxides, metal nitrides,
and metal oxynitrides.
In addition, each of the first and second thin film layers may be a
multilayer film including an organic layer/an inorganic layer/an
organic layer, an inorganic layer/an organic layer/an inorganic
layer, or the like which are laminated on the base material. In
this case, the inorganic layer mainly exhibits the gas barrier
properties. A preferable composition of the inorganic layer is any
of metal oxides, metal nitrides, metal oxynitrides, silicon oxides,
and silicon oxide carbides described below. The organic layer
relaxes a stress between the base material and the inorganic layer,
or produces an effect of smoothing the upper surface of the base
material by being embedded between the asperities and particles on
the upper surface. Further, the organic layer may have a water
capturing function. A preferable composition of the organic layer
is any of organic materials usable for a thermosetting adhesive, a
photocurable adhesive, a two-component curable adhesive, and the
like, which are mentioned below. Note that the kinds of the first
thin film layer 101(a) and the second thin film layer 101(b) may be
the same as or different from each other.
Then, the metal oxide, the metal nitride and the metal oxynitride
to be used for such a thin film layer is preferably deposited by a
method such as a sputtering method, a vacuum deposition method, an
ALD (atomic layer deposition) method, and an ion plating method,
from the viewpoint that higher water vapor permeation prevention
performance can be exhibited with a thinner film, and from the
viewpoints of transparency and the like. From the viewpoints of
ease of production and low production cost, the sputtering method
and the ALD method are more preferable.
Further, the thin film layer is more preferably a layer formed of a
thin film containing at least silicon and oxygen from the viewpoint
that the film can exhibit higher water vapor permeation prevention
performance and from the viewpoints of flexing endurance, ease of
production, and low production cost. Moreover, the layer formed of
a thin film containing silicon and oxygen is preferably a thin film
layer formed by using a plasma chemical vapor deposition method or
a thin film formation method of forming a precursor on a base
material surface and performing a plasma treatment. Among such thin
film layers, a particularly preferable thin film layer is a silicon
oxide-based thin film layer containing silicon, oxygen and carbon,
and satisfying all the following requirements (i) to (iii) in a
silicon distribution curve, an oxygen distribution curve, and a
carbon distribution curve, each of the silicon, oxygen, and carbon
distribution curves representing the relationship between the
distance from a surface of the layer in the film thickness
direction of the layer and corresponding one of the ratio of the
amount of silicon atoms to the total amount of silicon atoms,
oxygen atoms, and carbon atoms (the atomic ratio of silicon), the
ratio of the amount of oxygen atoms to said total amount (the
atomic ratio of oxygen), and the ratio of the amount of carbon
atoms to said total amount (the atomic ratio of carbon):
(i) the atomic ratio of silicon, the atomic ratio of oxygen, and
the atomic ratio of carbon satisfy, in any region corresponding to
90% or more of the film thickness of the layer, a requirement
represented by the following formula (1): (atomic ratio of
oxygen)>(atomic ratio of silicon)>(atomic ratio of carbon)
(1);
(ii) the carbon distribution curve has at least one extremum;
and
(iii) the absolute value of the difference between the maximum
value and the minimum value of the atomic ratio of carbon in the
carbon distribution curve is 5 at % or greater.
Such a silicon oxide-based thin film layer, first of all, is
required to satisfy the following. Specifically, in a silicon
distribution curve, an oxygen distribution curve, and a carbon
distribution curve, each of the silicon, oxygen, and carbon
distribution curves representing the relationship between the
distance from a surface of the layer in the film thickness
direction of the layer and corresponding one of the ratio of the
amount of silicon atoms to the total amount of silicon atoms,
oxygen atoms, and carbon atoms (the atomic ratio of silicon), the
ratio of the amount of oxygen atoms to said total amount (the
atomic ratio of oxygen), and the ratio of the amount of carbon
atoms to said total amount (the atomic ratio of carbon):
(i) in any region corresponding to 90% or more (more preferably 95%
or more, and particularly preferably 100%) of the thickness of the
layer, the atomic ratio of silicon, the atomic ratio of oxygen, and
the atomic ratio of carbon satisfy a requirement represented by the
following formula (1): (atomic ratio of oxygen)>(atomic ratio of
silicon)>(atomic ratio of carbon) (1). If the atomic ratio of
silicon, the atomic ratio of oxygen, and the atomic ratio of carbon
do not satisfy the requirement, the obtained gas-barrier multilayer
film has insufficient gas barrier properties.
Next, in such a silicon oxide-based thin film layer, (ii) the
carbon distribution curve needs to have at least one extremum. In
such a silicon oxide-based thin film layer, the carbon distribution
curve has more preferably at least two extrema, and particularly
preferably at least three extrema. If the carbon distribution curve
has no extremum, the obtained gas-barrier multilayer film exhibits
insufficient gas barrier properties when the film is bent.
Moreover, when the carbon distribution curve has at least three
extrema as described above, the absolute value of the difference in
distance from the surface of the thin film layer in the film
thickness direction of the thin film layer between each of the
extrema of the carbon distribution curve and any one of the extrema
adjacent to the former one is preferably 200 nm or less, and more
preferably 100 nm or less. Note that, in the present invention, an
extremum refers to a local maximum or a local minimum of the atomic
ratio of an element with respect to the distance from a surface of
the silicon oxide-based thin film layer in the film thickness
direction of the thin film layer. Moreover, in the present
invention, the local maximum refers to a point at which change of
the value of the atomic ratio of an element turns from increase to
decrease when the distance from the surface of the silicon
oxide-based thin film layer is changed and the value of the atomic
ratio of the element decreases by 3 at % or more in comparison to
the value of the atomic ratio of the element at that point when the
distance from the surface of the thin film layer in the film
thickness direction of the thin film layer is further changed by 20
nm from that point. Meanwhile, in the present invention, the local
minimum refers to a point at which the change of the value of the
atomic ratio of an element turns from decrease to increase when the
distance from the surface of the silicon oxide-based thin film
layer is changed and the value of the atomic ratio of the element
increases by 3 at % or more in comparison to the value of the
atomic ratio of the element at that point when the distance from
the surface of the thin film layer in the film thickness direction
of the thin film layer is further changed by 20 nm from that
point.
Moreover, in such a silicon oxide-based thin film layer, (iii) the
absolute value of the difference between the maximum value and the
minimum value of the atomic ratio of carbon in the carbon
distribution curve needs to be 5 at % or greater. In addition, in
such a thin film layer, the absolute value of the difference
between the maximum value and the minimum value of the atomic ratio
of carbon is more preferably 6 at % or greater, and particularly
preferably 7 at % or greater. If the absolute value is smaller than
5 at %, the gas barrier properties of the obtained gas-barrier
multilayer film are insufficient when the film is bent.
Moreover, in the silicon oxide-based thin film layer, the oxygen
distribution curve of the thin film layer preferably has at least
one extremum, more preferably at least two extrema, and
particularly preferably at least three extrema. If the oxygen
distribution curve has no extremum, the obtained gas-barrier
multilayer film tends to exhibit low gas barrier properties when
the film is bent. Moreover, when the oxygen distribution curve has
at least three extrema as described above, the absolute value of
the difference in distance from the surface of the thin film layer
in the film thickness direction of the thin film layer between each
of the extrema of the carbon distribution curve and any one of the
extrema adjacent to the former one is preferably 200 nm or less,
and more preferably 100 nm or less.
Moreover, in the silicon oxide-based thin film layer, the absolute
value of the difference between the maximum value and the minimum
value of the atomic ratio of oxygen in the oxygen distribution
curve of the thin film layer is preferably 5 at % or greater, more
preferably 6 at % or greater, and particularly preferably 7 at % or
greater. If the absolute value is smaller than the lower limit, the
gas barrier properties of the obtained gas-barrier multilayer film
tend to be low when the film is bent.
In the silicon oxide-based thin film layer, the absolute value of
the difference between the maximum value and the minimum value of
the atomic ratio of silicon in the silicon distribution curve of
the thin film layer is preferably smaller than 5 at %, more
preferably smaller than 4 at %, and particularly preferably smaller
than 3 at %. If the absolute value exceeds the upper limit, the gas
barrier properties of the obtained gas-barrier multilayer film tend
to decrease.
Moreover, in the silicon oxide-based thin film layer, in an
oxygen-carbon distribution curve which represents the relationship
between the distance from the surface of the layer in the film
thickness direction of the layer and the ratio of the total amount
of oxygen atoms and carbon atoms to the total amount of silicon
atoms, oxygen atoms, and carbon atoms (the atomic ratio of oxygen
and carbon), the absolute value of the difference between the
maximum value and the minimum value of the total atomic ratio of
oxygen and carbon is preferably smaller than 5 at %, more
preferably smaller than 4 at %, and particularly preferably smaller
than 3 at %. If the absolute value exceeds the upper limit, the gas
barrier properties of the obtained gas-barrier multilayer film tend
to decrease.
The silicon distribution curve, the oxygen distribution curve, the
carbon distribution curve, and the oxygen-carbon distribution curve
can be produced by the so-called XPS depth profile measurement; in
the XPS depth profile measurement, measurement by X-ray
photoelectron spectroscopy (XPS) and noble gas ion sputtering using
argon or the like are conducted in combination to conduct a
sequential surface composition analysis while the inside of a
sample is being made to be exposed. A distribution curve obtained
by such XPS depth profile measurement can be produced by, for
example, taking the atomic ratio of each element (unit: at %) on
the vertical axis and the etching time (sputtering time) on the
horizontal axis. Note that, in an element distribution curve where
the horizontal axis represents the etching time as described above,
the etching time approximately correlates to the distance from the
surface of the thin film layer in the film thickness direction of
the thin film layer in the film thickness direction. Hence, a
distance from the surface of the thin film layer calculated from a
relationship between the etching rate and the etching time employed
in the XPS depth profile measurement can be employed as the
"distance from the surface of the thin film layer in the film
thickness direction of the thin film layer". Moreover, regarding
the sputtering method employed for the XPS depth profile
measurement, it is preferable to employ a noble gas ion sputtering
method using argon (Ark) as an etching ion species, and set the
etching rate to 0.05 nm/sec (in terms of SiO.sub.2 thermally
oxidized film).
Moreover, from the viewpoint of forming a silicon oxide-based thin
film layer having gas barrier properties which are excellent and
constant over the entire film surface, the thin film layer is
preferably substantially uniform in the film surface direction (the
direction in parallel to a surface of the thin film layer). In this
DESCRIPTION, the phrase "the silicon oxide-based thin film layer is
substantially uniform in the film surface direction" means that
when the oxygen distribution curves, the carbon distribution
curves, and the oxygen-carbon distribution curves are produced for
any two measurement points on the film surface of the thin film
layer by XPS depth profile measurement, the carbon distribution
curves obtained at the two measurement points have the same number
of extrema and the carbon distribution curves have the same
absolute value of the difference between the maximum value and the
minimum value of the atomic ratio of carbon or have absolute values
which are different by 5 at or less.
Moreover, in the silicon oxide-based thin film layer, the carbon
distribution curve of the layer is preferably substantially
continuous. In this DESCRIPTION, the phrase "the carbon
distribution curve is substantially continuous" means that no
portion exists at which the atomic ratio of carbon changes
discontinuously in the carbon distribution curve. Specifically, the
relationship between the distance (x, unit: nm) from the surface of
at least one layer of the thin film layer(s) in the film thickness
direction of the layer calculated from the etching rate and the
etching time, and the atomic ratio of carbon (C, unit: at %)
satisfy a requirement represented by the following formula (F1):
(dC/dx).ltoreq.0.5 (F1).
Moreover, when the atomic ratio of silicon, the atomic ratio of
oxygen, and the atomic ratio of carbon in the silicon, oxygen, and
carbon distribution curves satisfy the requirement represented by
the above-described formula (1) in any region corresponding to 90%
or more of the film thickness of the layer, the atomic ratio of the
content of silicon atoms in the layer to the total amount of
silicon atoms, oxygen atoms, and carbon atoms is preferably 25 to
45 at %, and more preferably 30 to 40 at %. In addition, the atomic
ratio of the content of oxygen atoms in the silicon oxide-based
thin film layer to the total amount of silicon atoms, oxygen atoms,
and carbon atoms is preferably 33 to 67 at %, and more preferably
45 to 67 at %. Moreover, the atomic ratio of the content of carbon
atoms in the silicon oxide-based thin film layer to the total
amount of silicon atoms, oxygen atoms, and carbon atoms is
preferably 3 to 33 at %, and more preferably 3 to 25 at %.
Moreover, when the atomic ratio of silicon, the atomic ratio of
oxygen, and the atomic ratio of carbon in the silicon, oxygen, and
carbon distribution curves satisfy the requirement represented by
the above-described formula (2) in any region corresponding to 90%
or more of the thickness of the layer, the atomic ratio of the
content of silicon atoms in the layer to the total amount of
silicon atoms, oxygen atoms, and carbon atoms is preferably 25 to
45 at %, and more preferably 30 to 40 at %. In addition, the atomic
ratio of the content of oxygen atoms in the silicon oxide-based
thin film layer to the total amount of silicon atoms, oxygen atoms,
and carbon atoms is preferably 1 to 33 at %, and more preferably 10
to 27 at %. Moreover, the atomic ratio of the content of carbon
atoms in the silicon oxide-based thin film layer to the total
amount of silicon atoms, oxygen atoms, and carbon atoms is
preferably 33 to 66 at %, and more preferably 40 to 57 at %.
In addition, the silicon oxide-based thin film layer is preferably
a layer formed by a plasma chemical vapor deposition method. Such a
thin film layer formed by the plasma chemical vapor deposition
method is more preferably a layer formed by a plasma chemical vapor
deposition method in which the base material is placed on the pair
of film forming rolls and plasma is generated by performing
discharge between the pair of film forming rolls. In addition,
during the discharge between the pair of film forming rolls as
described above, the polarities of the pair of film forming rolls
are preferably reversed alternately. Moreover, as a film-forming
gas used for the plasma chemical vapor deposition method, a gas
containing an organosilicon compound and oxygen is preferable. The
content of oxygen in the film-forming gas is preferably not more
than a theoretical amount of oxygen necessary to completely oxidize
the entire amount of the organosilicon compound in the film-forming
gas. In addition, the thin film layer is preferably a layer formed
by a continuous film formation process. Note that such a silicon
oxide-based thin film layer may be produced by using a method
described in JP 2011-73430 A.
Further, preferably at least one of the first thin film layer
101(a) and the second thin film layer 101(b) is a silicon
oxide-based thin film layer because higher water vapor permeation
prevention performance can be exhibited. More preferably, both of
them are silicon oxide-based thin film layers.
Moreover, the gas-barrier multilayer film (transparent support
substrate 1) in the embodiment illustrated in FIG. 2 includes an
adhesive layer 102. Preferable adhesives usable to form the
adhesive layer 102 are curable adhesives such as thermosetting
adhesives, photocurable adhesives, and two-component curable
adhesives from the viewpoints of ease of production and
low-volatility component.
As such a thermosetting resin adhesive, any publicly-known
thermosetting resin adhesive may be used as needed without
particular limitation. As such thermosetting resin adhesives, there
are epoxy adhesives, acrylate adhesives, and so on. An example of
such epoxy-based adhesives is an adhesive containing an epoxy
compound selected from bisphenol A epoxy resins, bisphenol F epoxy
resins, and phenoxy resins. Meanwhile, an example of such
acrylate-based adhesives is an adhesive containing a monomer as a
main component selected from acrylic acid, methacrylic acid, ethyl
acrylate, butyl acrylate, 2-hexyl acrylate, acrylamide,
acrylonitrile, hydroxyl acrylate, and the like, and a monomer
copolymerizable with the main component.
Meanwhile, as the photocurable adhesive, any publicly-known
photocurable adhesive can be used as needed without particular
limitation, and may be, for example, any of radical adhesives,
cationic adhesives, and the like. Examples of such radical
adhesives include adhesives containing epoxy acrylate, ester
acrylate, ester acrylate, and the like. Then, examples of such
cationic adhesives include adhesives containing epoxy-based resins,
vinyl ether-based resins, and the like.
Moreover, the adhesive layer 102 may further contain a moisture
adsorbent (so-called a drying agent or desiccant), a bluing agent,
an ultraviolet absorber, an antioxidant, or the like. When the
multilayer film is used as a substrate of an organic EL for
illumination, the adhesive layer 102 may contain a dye or pigment
of the same color as the color of light emitted by the organic EL,
or may contain a dye or pigment of a different color from the color
of light emitted by the organic EL with the intention of producing
a color mixing effect. Further, in order to produce a light
scattering effect or a light extraction effect, the adhesive layer
102 may contain inorganic particles or the like having a different
optical refraction index from that of the adhesive layer.
It is preferable that the adhesive layer 102 contain a moisture
adsorbent with the following intentions. Specifically, when the
adhesive contains moisture, the moisture adsorbent can reduce the
moisture in the adhesive layer and thereby satisfactorily inhibit
the performance from deteriorating due to the moisture generated
from the adhesive layer. In addition, the moisture adsorbent allows
the gas-barrier multilayer film to exhibit higher hygroscopic
performance and thereby allows the gas-barrier multilayer film to
exhibit higher water vapor permeation prevention performance. Such
a moisture adsorbent (drying agent) is not particularly limited,
but may be, for example, a metal oxide such as silica gel, zeolite
(molecular sieve), magnesium oxide, calcium oxide, barium oxide, or
strontium oxide; a metal hydroxide such as dried aluminum
hydroxide; or the like. Among these moisture adsorbents (drying
agents), calcium oxide and dried aluminum hydroxide are
particularly preferable from the viewpoints of sufficiently high
light transmittance and the like.
As such a moisture adsorbent (drying agent), a particulate
adsorbent is preferable. Such a particulate moisture adsorbent
(drying agent) has an average particle diameter in the range of
preferably 0.01 to 10 .mu.m (more preferably 0.01 to 5 .mu.m, and
even more preferably 0.1 to 5 .mu.m). When the average particle
diameter is less than 0.01 .mu.m, the primary particles tend to
aggregate easily and form large aggregated particles (secondary
particles). In addition, having too strong hygroscopic power, the
moisture adsorbent, when added to the adhesive layer, already
completes moisture absorption fully and cannot exhibit the
hygroscopic ability anymore. On the other hand, when the average
particle diameter exceeds 10 .mu.m, the adhesive tends to have
difficulty in forming a smooth layer when formed into a film form,
and to fail to obtain a sufficient hygroscopic ability.
Moreover, the content of such a moisture adsorbent (drying agent)
is not particularly limited, but is preferably 5 to 50% by mass in
the adhesive (more preferably 10 to 30% by mass). If the content of
the absorbent (drying agent) is less than the above lower limit,
the moisture supply ability tends to be lowered because the
adsorbent fully absorbs the moisture contained in the adhesive. On
the other hand, when the content exceeds the above upper limit, the
light transmittance tends to decrease, and accordingly reduce light
extraction from the luminescent layer of the organic EL.
In addition, such an adhesive layer 102 preferably contains, for
example, a bluing agent depending on the use of the organic EL
device. Such a bluing agent is not particularly limited, but any
publicly-known bluing agent can be suitably used as needed such for
example as Macrolex Violet B and Macrolex Blue RR manufactured by
Bayer AG and Terazole Blue RLS and Triazole Blue RLS manufactured
by Sandoz Ltd. Moreover, Solvent Violet-3, Solvent Blue-94, Solvent
Blue-78, Solvent Blue-95, Solvent Violet-13 and the like according
to color index classification can also be used.
Then, the thickness of such an adhesive layer 102 is not
particularly limited. However, if a solid content such as powder
(for example, the foregoing moisture adsorbent (drying agent),
optical refraction index control particles or the like) is added to
the adhesive and particles constituting the powder (powder
particles) do not aggregate in nature, the thickness of the
adhesive layer 102 is preferably approximately equal to the maximum
diameter of the primary particle diameter of the powder particles,
and more preferably 1 to 20 .mu.m in general in this case. On the
other hand, in the case where the powder particles aggregate in
nature, the thickness of the adhesive layer 102 is preferably
approximately equal to the maximum diameter of the secondary
particle diameter of the powder particles, and more preferably 5 to
50 .mu.m in general in this case. Alternatively, if no solid
content such as powder is added to the adhesive and the adhesive
layer 102 is formed by applying and drying the adhesive, the
thickness of the adhesive layer 102 is preferably 0.2 to 30 .mu.m
and more preferably 0.5 to 10 .mu.m from the viewpoints of adhesion
strength and processing workability. Instead, if an adhesive in a
film form (adhesive film) is used to form the adhesive layer 102,
the thickness of the adhesive layer 102 is preferably 1 to 100
.mu.m and more preferably 5 to 50 .mu.m from the viewpoint of
processing workability.
In addition, an adhesive processed in a film form (sheet) may be
used to form such an adhesive layer. In this case, such an adhesive
film with a film thickness of 100 .mu.m in an environment at
60.degree. C. and 90 RH % preferably has a water vapor permeability
of 100 g/m.sup.2/day or less (more preferably 30 g/m.sup.2/day or
less), and a light transmittance of 70% or more (more preferably
80% or more). If the water vapor permeability exceeds the above
upper limit, the moisture permeation from portions of the end faces
of the gas-barrier multilayer film where the adhesive portions are
exposed increases so much that a time until the moisture content in
the first base material reaches the saturated content tends to be
shortened, and consequently the storage life of the organic EL
tends to be shorten. Meanwhile, if the light transmittance is less
than the above lower limit, the internal light cannot be
sufficiently emitted to the outside, whereby the light emission
efficiency of the organic EL tends to be lowered. Note that, as the
water vapor permeability, it is possible to employ a value measured
by, for example, a calcium-light transmittance method (when
absorbing moisture, Ca metal is changed to calcium oxide, calcium
hydroxide or the like, and accordingly the light transmittance
changes), a MOCON's water vapor transmission rate (WVTR) testing
system, or the like. Meanwhile, the light transmittance can be
measured by an optical thin film metrology system device
manufactured by Film-Tek Corporation (United States) or the
like.
Still further, the adhesive layer is preferably a layer in which
the ratio of the optical refraction index of the first base
material layer 100(a) to the optical refraction index of the
adhesive layer ([optical refraction index of first base material
layer 100(a)]/[optical refraction index of adhesive layer]) is 0.88
to 1.18 (more preferably 1.01 to 1.11). If the ratio between the
optical refraction indexes is less than the above lower limit, the
refraction index of the adhesive layer needs to be further
increased, and the light emitted to the outside tends to decrease
when the optical refraction index of the adhesive layer is more
than that of the second thin film layer. On the other hand, if the
ratio exceeds the above upper limit, the light is largely reflected
at the interface between the first base material and the adhesive
layer, and accordingly the emission of light from the luminescent
layer to the outside tends to decrease. Note that the optical
refraction index can be measured by, for example, an optical thin
film metrology system device manufactured by Film-Tek Corporation
(United States), a general-purpose ellipsometeror, or the like.
Additionally, the gas-barrier multilayer film (transparent support
substrate 1) in the embodiment illustrated in FIG. 2 has the
multilayer structure in which the thin film layer 101(a), the base
material layer 100(a), the adhesive layer 102, the thin film layer
101(b), and the base material layer 100(b) are layered in this
order. With this multilayer structure, the light emitting element
to be described later is directly stacked on the surface of the
thin film layer, and the thin film layer can highly inhibit water
vapor from permeating the inside of the element.
The entire thickness of such a gas-barrier multilayer film
(transparent support substrate 1) is preferably 50 to 300 .mu.m and
more preferably 100 to 2500 .mu.m. If a gas-barrier multilayer film
with a film thickness less than the above lower limit is formed to
be a long base material, the film tends to be difficult to control
because the film is more likely to be wrinkled or twisted in
manufacturing steps of an organic EL device. On the other hand, if
the thickness of a base material layer is larger than the foregoing
upper limit, the film tends to absorb an increased amount of light
and thereby to reduce the light emission from the luminescent layer
to the outside. In addition, if the thickness of the gas-barrier
multilayer film is larger than the above upper limit, water vapor
is more likely to permeate the base material layer from directions
parallel to the surface of the gas-barrier multilayer film (from
the end sides: directions perpendicular to the end faces). For this
reason, for example, if a base material and the like in a dry state
are used in the production of the gas-barrier multilayer film, the
dry state of the base material tends to be difficult to keep
satisfactorily for a long period of time.
Moreover, the gas-barrier multilayer film preferably has such a
hygroscopicity that the film can absorb water in a weight of 0.1%
by mass or more of its own weight (the mass of the gas-barrier
multilayer film itself) (more preferably 0.2% by mass or more of
its own weight). If this hygroscopicity is less than the above
lower limit, it tends to be difficult for the gas-barrier
multilayer film to exhibit further higher moisture permeation
prevention performance. The hygroscopicity of the gas-barrier
multilayer film is preferably 5% by mass or less of its own weight
from the viewpoints of a load applied on the base material during
drying, a time period required for drying, a decrease in the
adhesiveness of the adhesive layer with an increase in the amount
of the hygroscopic agent, and so on. This hygroscopicity is more
preferably 3% by mass or less of its own weight, and even more
preferably 2% by mass or less of its own weight.
Here, the hygroscopicity of the gas-barrier multilayer film can be
measured as follows. Specifically, first, a gas-barrier multilayer
film (50 mm square film) is prepared with both a length of 50 mm
and a width of 50 mm (50 mm square) for measurement of the
hygroscopicity of the gas-barrier multilayer film. Next, the 50 mm
square film is cut at 1 mm pitches into rectangular pieces. Thus,
rectangular samples in the size with a length of 50 mm and a width
of 1 mm are prepared. Next, the mass (unit: g) of the rectangular
samples (50 samples) with a length of 50 mm and a width of 1 mm is
precisely measured down to four decimal places at a room
temperature (25.degree. C.) in atmospheric air in a thermostatic
chamber. The mass thus measured is used as the film's own weight
(W1: an initial mass before use) mentioned above. Subsequently, the
50 samples are allowed to stand in an atmosphere at constant
temperature and constant humidity (25.degree. C., humidity of 50%,
a humidity ratio of 10 g/kg), and the mass of the samples is
precisely measured down to four decimal places every 24 hours. Such
mass measurement is conducted until the mass of the samples (50
samples) becomes constant. Then, the mass taking the constant value
is used as Wn. In the present invention, a value obtained by
calculating the following formula: [Ratio of moisture absorption
Bn]={(Wn-W1)/W1}.times.100, based on the values Wn and W1 thus
obtained is used as the hygroscopicity of the gas-barrier
multilayer film.
Here, this hygroscopicity is a hygroscopicity basically exhibited
based on the hygroscopic performance of the base material layer
disposed between the first and second thin film layers having gas
barrier properties. In order that the base layer disposed between
the first and second thin film layers can absorb moisture more
sufficiently, the gas-barrier multilayer film is preferably
produced by forming, as the base material layer, a layer made of a
base material composed of a polymer containing heteroatoms other
than hydrogen (more preferably a polyester having an ester bond,
and even more preferably PET or PEN), and by disposing the
sufficiently dried base material between the first and second thin
film layers in the production of the gas-barrier multilayer
film.
Moreover, in the gas-barrier multilayer film (transparent support
substrate 1) in the embodiment illustrated in FIG. 2, a ratio of
the total value of the thicknesses of all the base material layers
included in the film to the entire thickness of the film ({[total
value of thicknesses of all base material layers]/[entire thickness
of gas-barrier multilayer film]}.times.100) is preferably 90% or
more and is more preferably 95% or more. If this ratio is less than
the above lower limit, the gas-barrier multilayer film tends to
have low flexibility, or be reduced in the productivity because the
base material is deformed due to a stress applied from the thin
film layer formed on the base material.
Further, a ratio of the total value of the thicknesses of all the
base material layers present between the first thin film layer and
the second thin film layer to the thickness of all the base
material layers present in the gas-barrier multilayer film
(transparent support substrate 1) in the embodiment illustrated in
FIG. 2 ({[total value of thicknesses of all base material layers
present between first thin film layer and second thin film
layer]/[thickness of all base material layers present in
gas-barrier multilayer film]}.times.100) is preferably 50% or more,
and is more preferably 90% or more in particular. If the ratio of
the thickness of the base material layer(s) between the thin film
layers is less than the above lower limit, it tends to be difficult
to exhibit sufficiently high hygroscopicity when the base material
is dried and is used to exhibit the hygroscopicity.
Moreover, a ratio of the thickness of the base material layer
present between the first thin film layer and the second thin film
layer to the entire thickness of the gas-barrier multilayer film
(transparent support substrate 1) in the embodiment illustrated in
FIG. 2 ({[thickness of base material layer present between first
thin film layer and second thin film layer]/[entire thickness of
gas-barrier multilayer film]}.times.100) is preferably 50% or more,
and is more preferably 90% or more in particular. If the ratio of
the thickness of the base material layer between the thin film
layers is less than the above lower limit, the mechanical strength
of a first film member on which an organic EL element is to be
formed tends to be lowered and accordingly increase the possibility
that the first base material may be broken, for example, in
consecutive steps, and it tends to be difficult to exhibit a
sufficiently high hygroscopicity when the base material is dried
and is used to exhibit the hygroscopicity.
Further, when the gas-barrier multilayer film (transparent support
substrate 1) is used in an organic EL device lamp and display, the
lower a value of yellowness index YI, the more preferable. The
yellowness index YI is more preferably 10 or less and even more
preferably 5 or less. The yellowness index YI can be measured in
accordance with JIS K 7373: 2006 by using, as a measurement
apparatus, a spectrophotometer capable of calculating tristimulus
values XYX.
Further, when the gas-barrier multilayer film (transparent support
substrate 1) is used in an organic EL device lamp and display, the
higher the total luminous transmittance, the more preferable. From
this viewpoint, the total luminous transmittance of the gas-barrier
multilayer film is more preferably 80% or more and even more
preferably 85% or more. Here, this total luminous transmittance can
be measured in accordance with JIS K 7375: 2008 by using, as a
measurement apparatus, a transmission measurement apparatus
including an integrating-sphere photometer.
Further, when the gas-barrier multilayer film (transparent support
substrate 1) is used as a substrate for an organic EL device for an
image display apparatus, the lower the haze, the more preferable.
The haze is more preferably 10% or less, and even more preferably
5% or less. Meanwhile, when the gas-barrier multilayer film is used
as a substrate for an organic EL device for an illumination
apparatus, the haze does not matter very much from the viewpoint of
the intended use. Rather, in the case where the light emission of
an organic EL is uneven due to density variation and unevenness of
the light emitting surface, the higher haze can make the unevenness
in the light emission less noticeable. From this viewpoint, the
gas-barrier multilayer film even with a high haze may be preferably
used. Thus, the gas-barrier multilayer film (transparent support
substrate 1) can be used with appropriate modification in which the
characteristics thereof are designed as needed depending on an
intended use of an organic EL device.
As a method suitably usable to produce the gas-barrier multilayer
film (transparent support substrate 1) illustrated in FIG. 2, it is
preferable to employ, for example, a method including a step (step
(A)) of preparing: a first film member which includes a first base
material layer and a first thin film layer formed on at least one
of the surfaces of the first base material layer and having gas
barrier properties; and a second film member which includes a
second base material layer and a second thin film layer formed on
at least one of the surfaces of the second base material layer and
having gas barrier properties, and a step (step (B)) of obtaining a
gas-barrier multilayer film by stacking and bonding the second thin
film layer of the second film member onto the surface of the base
material layer of the first film member with an adhesive.
Hereinafter, these steps (A) and (B) will be described one by
one.
(Step (A))
Step (A) is a step of preparing the first and second film members.
A method for preparing these first and second film members is not
particularly limited, but any publicly-known method can be employed
as needed. For example, the preparation may be made by employing an
appropriate method capable of producing film members (first and
second film members) each including a base material layer and a
thin film layer having gas barrier properties by forming the thin
film layer on at least one of the surfaces of the base material, or
film members (first and second film members) may be prepared by
using commercially available film members (multilayer bodies) each
including a base material and a thin film layer having gas barrier
properties. In the case of forming the thin film layer on the base
material, any publicly-known method capable of depositing such a
thin film layer may be employed as needed, but it is preferable to
employ a plasma chemical vapor deposition method (plasma CVD) from
the viewpoint of gas barrier properties. Here, the plasma chemical
vapor deposition method may be a plasma chemical vapor deposition
method of a penning discharge plasma type. Instead, as the method
for forming the thin film layer on the base material, it is
preferable to employ a method described in JP 2011-73430A. With
this method, the foregoing silicon oxide-based thin film layer can
be formed on the base material efficiently.
(Step (B))
Step (B) is a step of obtaining the gas-barrier multilayer film by
stacking and bonding the second thin film layer of the second film
member onto the surface of the base material layer of the first
film member with an adhesive.
In this way where the second thin film layer of the second film
member is stacked and bonded onto the surface of the base material
layer of the first film member with the adhesive, the films thus
stacked can have a multilayer structure in which the first thin
film layer, the first base material layer, an adhesive layer, the
second thin film layer, and the second base material layer are
layered in this order.
A method for bonding the first and second film members with an
adhesive as described above is not particularly limited, but any
publicly-known method capable of bonding film members with an
adhesive may be employed as needed. For example, it is possible to
employ an appropriate method such as a bonding method including
forming a stack in which a sheet made of an adhesive having a low
melting point is arranged between the first and second film
members, and melting the sheet by heating, and a method of bonding
the first and second film members by applying an adhesive to the
surfaces to be bonded. Here, temperature and other conditions
usable in these methods are not also particularly limited, but
optimum conditions may be employed as needed depending on the kinds
of the first and second film members, the kind of the adhesive, and
so on. Further, it is preferable that this adhesive contain a
moisture adsorbent additionally, because the adhesive can exhibit a
higher hygroscopicity. Also, the method for applying the adhesive,
the thickness of the adhesive applied, and the like are not
particularly limited. Specifically, in order that the foregoing
layer made of the adhesive can be produced, it is possible to
employ, as needed, an optimum method from among publicly-known
coating methods (for example, coating methods such as doctor blade,
wire bar, die coater, comma coater, gravure coater, screen
printing, and ink jet methods), and also its conditions.
Additionally, in the case of bonding the first film member and the
second film member together as described above, it is preferable to
perform a step of drying at least the first film member (one of the
film members) beforehand. If the first film member are the second
film member are bonded together while the above requirement is
satisfied, it is also possible to more efficiently produce the
gas-barrier multilayer film having a sufficient hygroscopicity
(preferably a hygroscopicity capable of absorbing water in a weight
of 0.1% by mass or more of its own weight).
A method (drying method) usable as the step of drying such a film
member is not particularly limited, but any publicly-known method
capable of drying such a film member may be employed as needed,
and, for example, vacuum drying, heat drying, vacuum heating
drying, and other methods may be employed as needed. Among these
drying methods, the vacuum heating drying which is a combination of
vacuum drying and heat drying is the most preferable from the
viewpoint of drying speed. Moreover, conditions (heating condition,
pressure condition, and others) for drying by the vacuum drying,
the heat drying, or the vacuum heating drying are not particularly
limited, but may be set as needed to conditions that enable drying
of the film member. Here, in the case where the drying method
includes a heating step, the heating temperature is set to
preferably 50.degree. C. or higher and particularly preferably
100.degree. C. or higher because the film member can be dried more
efficiently. If the drying method is a step of drying while heating
(for example, in the case of employing the heat drying or the
vacuum heating drying), the upper limit of the heating temperature
may be set as needed depending on the kind of the base material and
others, and is not particularly limited. However, from the
viewpoint of more satisfactorily preventing a deformation of the
base material due to a high temperature, the upper limit is set to
preferably 200.degree. C. or lower, and more preferably 150.degree.
C. or lower.
Instead, if the drying method is a method of drying under a vacuum
condition (for example, in the case of employing the vacuum drying
or the vacuum heating drying), the pressure condition may just be
set to a pressure lower than an atmospheric pressure of 760 mmHg
(101325 Pa), and is not particularly limited. However, the pressure
condition is set to a pressure lower than 76 mmHg (10132.5 Pa)
preferably, and a pressure lower than 7.6 mmHg (1013.25 Pa) more
preferably. Note that the "vacuum drying" in this DESCRIPTION may
be any drying under reduced pressure lower than the atmospheric
pressure of 760 mmHg (101325 Pa).
In the case of employing such a drying method, a drying period for
drying the film member is not particularly limited. Depending on
the conditions employed, an execution period (drying period) may be
changed as needed such that the film member can be dried
sufficiently. For example, in the case of drying under the
foregoing heating temperature condition and pressure condition
(vacuum condition) (the case of vacuum heating drying), the drying
period is set to preferably 3 hours (180 minutes) or longer, and
more preferably 6 hours (360 minutes) or longer from the viewpoint
that the film member can be turned in a more sufficiently dry
state. Here, this drying period may be set as needed depending on
the thickness and kind of the base material, and so on.
In the case where at least the first film member is dried by the
drying step, it is preferable to bond the first and second film
members together while a time period for which the dried film
member is exposed to an atmosphere having a humidity ratio of 10
g/kg or more is restricted to shorter than one hour.
In bonding the first film member and the second film member
together, it is preferable to perform the bonding with the
foregoing adhesive containing the moisture adsorbent. In the case
of bonding with the adhesive containing the moisture adsorbent as
described above, basically the adhesive layer containing the
moisture adsorbent is also present together with the base material
layer between the thin film layers. If the adhesive layer
containing the moisture adsorbent is inserted between the thin film
layers, it is possible to dry the first base material layer
disposed between the first and second thin film layers with the
moisture adsorbent in the adhesive layer. For this reason, in the
gas-barrier multilayer film thus obtained, the base material layer
present between the thin film layers can be dried also after the
bonding, and thus the base material layer can be made to exhibit
the hygroscopicity. Since the gas-barrier multilayer film thus
obtained includes the adhesive layer containing the moisture
adsorbent between the thin film layers, the moisture adsorbent in
the adhesive layer itself can be also made to exhibit the
hygroscopicity. Thus, the bonding of the first film member and the
second film member together with the adhesive layer containing the
moisture adsorbent also makes it possible to more efficiently form
the gas-barrier multilayer film having a sufficient hygroscopicity
(preferably a hygroscopicity capable of absorbing water in a weight
of 0.1% by mass or more of its own weight). Here, in the case of
bonding the first film member and the second film member together
with the adhesive layer containing the moisture adsorbent as
described above, the step of drying at least the first film member
may be or may not be included before the bonding of the first and
second film members, but it is preferable to include the drying
step from the viewpoints that the higher hygroscopicity can be
exhibited, and the gas-barrier multilayer film (transparent support
substrate 1) can be made to exhibit much higher water vapor
permeation prevention performance.
Here, in the step of bonding the first and second film members, the
first and second film members are preferably bonded together under
a temperature condition of 20 to 150.degree. C. If the temperature
exceeds the above upper limit, the base material tends to have a
damage such as a deformation. On the other hand, if the temperature
is lower than the above lower limit, the adhesion between the
adhesive and the base material or the thin film layer tends to be
lowered to increase a possibility of the occurrence of water vapor
permeation from the interface.
By performing step (A) and step (B) as described above, it is
possible to obtain the gas-barrier multilayer film (transparent
support substrate 1) in the embodiment illustrated in FIG. 2, which
is suitably usable in the present invention.
Note that the terms "first", "second", and so on in this
DESCRIPTION are used for the sake of convenience for explaining two
or more same or equivalent elements (for example, base material
layers, thin film layers, film members, and so on), and there is no
particular meaning in the numbers indicated by these terms and the
order in the explanation (the numbers do not indicate superiority
or inferiority). These elements may be the same as or different
from each other.
In addition, step (B) may be performed after the light emitting
element 2 is formed on the first thin film layer of the first film
member as will be described later. Alternatively, step (B) may be
performed before the formation of the light emitting element 2, and
thereafter the light emitting element 2 may be formed. Instead, the
light emitting element 2 may be formed after the drying step of the
base material layer of the first film member in the step (B) is
performed, or the drying step may be formed after the light
emitting element 2 is formed.
[Light Emitting Element 2]
The light emitting element 2 includes a pair of electrodes and a
luminescent layer disposed between the electrodes. The pair of
electrodes (a first electrode 201 and a second electrode 203) and
the luminescent layer 202 disposed between the electrodes, which
constitute the light emitting element 2, are not particularly
limited, but any electrodes and luminescent layer used in
publicly-known organic EL devices may be used as needed. For
example, the electrode on the light extraction side may be made
transparent or semi-transparent, and the luminescent layer may be
formed by using a low molecular and/or high molecular organic
luminescent material. Hereinafter, the first electrode 201, the
luminescent layer 202, and the second electrode 203 will be
described one by one.
(First Electrode 201)
The first electrode 201 is one of anode and cathode electrodes. In
the light emitting element 2 in the embodiment illustrated in FIG.
1, the first electrode 201 is formed by using an optically
transparent electrode (transparent or semi-transparent electrode)
such that the light emitted from the luminescent layer 202 can be
outputted to the outside of the element 2. In the embodiment
illustrated in FIG. 1, the optically transparent first electrode
201 is used as an anode.
As such an optically transparent first electrode 201 (anode), a
thin film made of any of metal oxides, metal sulfides, metals and
so on may be used. A film with higher electrical conductivity and
higher light transmittance is more preferably employed. As the
electrode formed of a thin film made of any of metal oxides, metal
sulfides, metals and so on, there are, for example, thin films made
of indium oxide, zinc oxide, tin oxide, ITO, indium zinc oxide
(abbreviated as IZO), gold, platinum, silver, copper, and so on.
Then, a thin film made of ITO, IZO or tin oxide is more preferable
as such a thin film made of any of metal oxides, metal sulfides,
metals and so on. A method for producing such a thin film made of
any of metal oxides, metal sulfides, metals and so on is not
particularly limited, but any publicly-known method can be employed
as needed, and, for example, a vacuum deposition method, a
sputtering method, an ion plating method, a plating method, or the
like may be employed.
Instead, the first electrode 201 may be formed by using an organic
transparent electrically-conductive film made of polyaniline, a
derivative thereof, polythiophene, a derivative thereof, or the
like. Alternatively, the first electrode 201 may be a film-form
electrode (A) including an optically transparent resin and a
wire-shaped conductor disposed inside the optically transparent
resin and having electrical conductivity. As the optically
transparent resin, a resin having higher light transmittance is
more preferable, and for example, there are: polyolefin resins such
as low or high density polyethylene, ethylene-propylene copolymers,
ethylene-butene copolymers, ethylene-hexene copolymers,
ethylene-octene copolymers, ethylene-norbornene copolymers,
ethylene-dimethano-octahydronaphthalene copolymers, polypropylene,
ethylene-vinyl acetate copolymers, ethylene-methyl methacrylate
copolymers, and ionomer resin; polyester resins such as
polyethylene terephthalate, polybutylene terephthalate, and
polyethylene naphthalate; nylon-6, nylon-6,6, and metaxylene
diamine-adipic acid condensation polymers; amide resins such as
polymethylmethacrylimide; acrylic resins such as polymethyl
methacrylate; styrene-acrylonitrile resins such as polystyrene,
styrene-acrylonitrile copolymers, styrene-acrylonitrile-butadiene
copolymers, and polyacrylonitrile; hydrophobized cellulose resins
such as cellulose triacetate and cellulose diacetate;
halogen-containing resins such as polyvinyl chloride,
polyvinylidene chloride, polyvinylidene fluoride, and
polytetrafluoroethylene; hydrogen bonding resins such as polyvinyl
alcohol, ethylene-vinyl alcohol copolymers, and cellulose
derivatives; engineering plastic resins such as polycarbonate
resin, polysulfone resin, polyethersulfone resin,
polyetheretherketone resin, polyphenylene oxide resin,
polymethylene oxide resin, polyarylate resin, and liquid crystal
resin; and so on. Here, in the case of producing an organic layer
on the anode by a coating method or the like, the resin
constituting the first electrode 201 is preferably a thermosetting
resin, a photocurable resin, or a photoresist material from the
viewpoint that the resin is more unlikely to be dissolved into the
coating liquid.
Then, the wire-shaped conductor with a small diameter is
preferable. The diameter of the wire-shaped conductor is preferably
400 nm or smaller, more preferably 200 nm or smaller, and even more
preferably 100 nm or smaller. Since such a wire-shaped conductor
diffracts or scatters light passing through the first electrode
201, the wire-shaped conductor accordingly increases the haze value
of the first electrode 201 and reduces the light transmittance of
the first electrode 201. Use of a wire-shaped conductor having a
diameter approximately equal to or smaller than the wavelength of
visible light makes it possible to keep the haze value to visible
light low and to improve the light transmittance. Here, the
diameter of the wire-shaped conductor is preferably 10 nm or more,
because the wire-shaped conductor has too high resistance when
having too a small diameter. When an organic EL device is used in
an illumination apparatus, the first electrode 201 with a high haze
value is preferred to be used in some cases, because the
illumination apparatus can illuminate a wide range if the haze
value of the first electrode 201 is high to some extent. In this
way, the optical characteristics of the first electrode 201 can be
set as needed depending on an apparatus in which the organic EL
device is to be used.
Then, such a film-form electrode (A) may include a single
wire-shaped conductor or two or more wire-shaped conductors. The
wire-shaped conductor preferably forms a mesh structure in the
electrode (A). Specifically, in the electrode (A), it is preferable
that one or more wire-shaped conductors be arranged to be
intricately interlaced with each other across the entire resin,
thereby forming a mesh structure (a two-dimensionally or
three-dimensionally spread mesh structure formed by a single
wire-shaped conductor interlaced intricately, or multiple
wire-shaped conductors arranged in contact with each other).
Moreover, such a wire-shaped conductor may be, for example, in a
curved line shape or a needle-like shape. When conductors in a
curved line shape or a needle-like shape are arranged in contact
with each other to form a mesh structure, the first electrode 201
with low volume resistivity can be obtained. This mesh structure
may be a regular or irregular structure. It is possible to reduce
the volume resistivity of the first electrode 201 by using the
wire-shaped conductor(s) forming the mesh structure.
At least part of the wire-shaped conductor is preferably arranged
near the surface of the first electrode 201 opposite to the
transparent support substrate ion which the first electrode 201 is
placed (the surface beside the luminescent layer 202 in the present
embodiment). Such arrangement of the wire-shaped conductor can
reduce the resistance in the surface portion of the first electrode
201. Here, as preferably-usable materials for such a wire-shaped
conductor, there are metals with low resistance such for example as
Ag, Au, Cu, Al, and alloys thereof. The wire-shaped conductor can
be manufactured by, for example, a method according to N. R. Jana,
L. Gearheart and C. J. Murphy (Chm. Commun., 2001, p617 to p618) or
a method according to C. Ducamp-Sanguesa, R. Herrera-Urbina, and M.
Figlarz (J. Solid State Chem., Vol. 100, 1992, p272 to p280) or the
like. Then, such an electrode (A) may have the same structure as an
electrode described in Japanese Unexamined Patent Publication
Application No. 2010-192472 (JP 2010-192472 A) and the production
method thereof may also be a method described in JP 2010-192472
A.
Moreover, the film thickness of the first electrode 201 (anode) may
be set as needed by taking account of the required characteristics
and easiness of processes, and is, for example, 10 nm to 10 .mu.m,
preferably 20 nm to 1 .mu.m, and more preferably 50 nm to 500
nm.
(Luminescent Layer 202)
The luminescent layer 202 may be a layer made of a publicly-known
material usable for a luminescent layer (layer having a function to
emit light) of an organic EL device. The luminescent layer 202 is
preferably a luminescent layer made of an organic material,
although the material thereof and others are not particularly
limited. Such a luminescent layer made of an organic material is
not particularly limited, but is preferably, for example, a layer
formed of an organic substance (a low molecular compound and a high
molecular compound) which emits fluorescence or phosphorescence as
a luminescent material, and a dopant which assists the luminescent
material. Here, the high molecular compound mentioned here has a
number average molecular weight of 10.sup.3 or more in terms of
polystyrene. Although there is not a particular reason to define
the upper limit of this number average molecular weight, the upper
limit of the number average molecular weight in terms of
polystyrene is preferably 10.sup.8 or less, in general.
As such a luminescent material (an organic substance which emits
fluorescence or phosphorescence), there are, for example, dye-based
materials, metal complex-based materials, polymer-based materials,
and so on. Such dye-based materials, there are, for example,
cyclopendamine derivatives, tetraphenyl butadiene derivative
compounds, triphenylamine derivatives, oxadiazole derivatives,
pyrazolo quinoline derivatives, distyrylbenzene derivatives,
distyrylarylene derivatives, pyrrole derivatives, thiophene ring
compounds, pyridine ring compounds, perinone derivatives, perylene
derivatives, oligothiophene derivatives, oxadiazole dimers,
pyrazoline dimers, and so on.
As the metal complex-based materials, there are, for example, metal
complexes such as aluminum quinolinol complexes, benzoquinoline
beryllium complexes, benzoxazolyl zinc complexes, benzothiazole
zinc complexes, azomethyl zinc complexes, porphyrin zinc complexes,
and europium complexes, which each have, as a central metal, Al,
Zn, Be, or etc., or a rare earth metal such as Tb, Eu, Dy, or etc.,
and have, as a ligand, an oxadiazole structure, a thiadiazole
structure, a phenylpyridine structure, a phenylbenzoimidazole
structure, a quinoline structure, and so on.
Moreover, as the polymer-based materials, there are, for example,
polyparaphenylene vinylene derivatives, polythiophene derivatives,
polyparaphenylene derivatives, polysilane derivatives,
polyacetylene derivatives, polyfluorene derivatives,
polyvinylcarbazole derivative, materials obtained by polymerization
of the above-mentioned dye-based and metal complex-based
luminescent materials, and so on.
Among such luminescent materials, the materials which emit blue
light are distyrylarylene derivatives, oxadiazole derivatives and
polymers thereof, polyvinylcarbazole derivatives, polyparaphenylene
derivatives, polyfluorene derivatives, and the like. Among these,
polymer materials such as polyvinylcarbazole derivatives,
polyparaphenylene derivatives, and polyfluorene derivatives are
preferable.
Meanwhile, the luminescent materials which emit green light are
quinacridone derivatives, coumarin derivatives and polymers
thereof, polyparaphenylenevinylene derivatives, polyfluorene
derivatives, and the like. Among these, polymeric materials such as
polyparaphenylenevinylene derivatives and polyfluorene derivatives
are preferable.
In addition, the luminescent materials which emit red light are
coumarin derivatives, thiophene ring compounds and polymers
thereof, polyparaphenylenevinylene derivatives, polythiophene
derivatives, polyfluorene derivatives, and the like. Among these,
polymeric materials such as polyparaphenylenevinylene derivatives,
polythiophene derivatives, and polyfluorene derivatives are
preferable.
Here, a method for producing such a luminescent material is not
particularly limited, but any publicly-known method can be employed
as needed, and for example, a method described in Japanese
Unexamined Patent Application Publication No. 2012-144722 (JP
2012-144722 A) may be employed.
Further, it is preferable to add a dopant to the luminescent layer
202 for the purposes of improving the light emission efficiency,
changing the wavelength of light emitted, and doing the like.
Examples of such a dopant include perylene derivatives, coumarin
derivatives, rubrene derivatives, quinacridone derivatives,
squarylium derivatives, porphyrin derivatives, styryl dyes,
tetracene derivatives, pyrazolone derivatives, decacyclene,
phenoxazone, and the like. Note that the thickness of such a
luminescent layer is preferably about 20 to 2000 .ANG., in
general.
A method for forming such a luminescent layer 202 is not
particularly limited, but any publicly-known method can be employed
as needed. Among such methods for forming the luminescent layer
202, the formation by a coating method is preferable. The coating
method is preferable in that the production process can be
simplified, and the excellent productivity can be achieved. As such
a coating method, there are a casting method, a spin coating
method, a bar-coating method, a blade coating method, a roll
coating method, gravure printing, screen printing, an inkjet
method, and the like. In the case of forming a luminescent layer
using the coating method, the luminescent layer with a desired
thickness can be formed by: first preparing, as a coating liquid, a
composition in a solution state containing a luminescent substance
and a solvent; and applying this coating liquid to a desired layer
or electrode by using a predetermined one of the aforementioned
coating methods, followed by drying it.
(Second Electrode 203)
The second electrode 203 is an electrode having the opposite
polarity to the first electrode 201, and is arranged opposed to the
first electrode 201. In the embodiment illustrated in FIG. 1, the
second electrode is a cathode.
A material for such a second electrode 203 (cathode) is not
particularly limited, and any publicly-known material may be used
as needed. It is preferable to use a material having a small work
function, enabling easy injection of electrons into the luminescent
layer, and having high electrical conductivity. In addition, in the
organic EL device configured to take out light from the anode side
as in the embodiment illustrated in FIG. 1, a material having a
high visible light reflectance is preferable as the material for
the second electrode 203 (cathode) because light emitted from the
luminescent layer can be reflected to the anode side by the cathode
and thus taken out more efficiently.
Examples of materials usable for such a second electrode 203
(cathode) include alkali metals, alkaline earth metals, transition
metals, Group 13 metals of the periodic table, and so on. More
specifically, preferably usable materials for the second electrode
203 (cathode) include: metals such as lithium, sodium, potassium,
rubidium, cesium, beryllium, magnesium, calcium, strontium, barium,
aluminum, scandium, vanadium, zinc, yttrium, indium, cerium,
samarium, europium, terbium, and ytterbium; alloys of two or more
of the foregoing metals; alloys of one or more of the foregoing
metals and one of more of gold, silver, platinum, copper,
manganese, titanium, cobalt, nickel, tungsten, and tin; or graphite
or graphite intercalation compounds; and so on. Examples of the
alloys include magnesium-silver alloys, magnesium-indium alloys,
magnesium-aluminum alloys, indium-silver alloys, lithium-aluminum
alloys, lithium-magnesium alloys, lithium-indium alloys,
calcium-aluminum alloys, and so on.
Moreover, as the second electrode 203 (cathode), it is possible to
use a transparent electrically-conductive electrode made of an
electrically-conductive metal oxide, an electrically-conductive
organic substance, and the like. Specifically, the
electrically-conductive metal oxide may be any of indium oxide,
zinc oxide, tin oxide, ITO, and IZO, and the
electrically-conductive organic substance may be any of
polyaniline, derivatives thereof, polythiophene, derivatives
thereof, and the like. Here, the second electrode 203 (cathode) may
be formed of a multilayer body in which two or more layers are
layered. In addition, what is termed an electron injection layer
may be used as the cathode.
The film thickness of the second electrode 203 (cathode) may be
designed as needed by taking account of the required
characteristics and easiness of processes, and is not particularly
limited. However, the film thickness of the second electrode 203 is
preferably 10 nm to 10 .mu.m, preferably 20 nm to 1 .mu.m, and more
preferably 50 nm to 500 nm. As a method for producing such a second
electrode 203 (cathode), a vacuum deposition method, a sputtering
method, a lamination method in which a metal thin film is
thermocompression-bonded, or the like may be employed.
Note that, in the embodiment illustrated in FIG. 1, the second
electrode 203 (cathode) is electrically connected to a connecting
part (lead electrode 203(a)) with which the second electrode 203
(cathode) can be electrically connected to the outside. Here, in
the embodiment illustrated in FIG. 1, the lead electrode 203(a) is
made of the same material as the first electrode 201. Such a lead
electrode 203(a) may be produced and designed as needed by a
publicly-known method. For example, the lead electrode 203(a) can
be easily produced by depositing a pattern for the part to
constitute the lead electrode 203(a) together in the process of
forming the first electrode 201.
[Sealing Material Layer 3]
The sealing material layer 3 is disposed on the transparent support
substrate 1 so as to cover and seal the light emitting element 2.
Such a sealing material layer 3 is a layer disposed on the
transparent support substrate 1 so as to seal the light emitting
element 2, and a layer made of any publicly-known sealing material
(for example, an adhesive sheet having sufficiently low water vapor
permeation ability, or the like) may be used as needed. More
specifically, such a sealing material layer 3 is a sealing layer
covering an area around the light emitting element 2 on the
transparent support substrate 1 so as to prevent the light emitting
device from coming into contact with outside air. Here, in such
sealing, in order for the light emitting element 2 to function as
the light emitting device, the light emitting element 2 is sealed
excluding connecting parts for electrically connecting the pair of
electrodes to the outside [for example, parts of a connection wire
and the so-called lead electrode (in the embodiment illustrated in
FIG. 1, these parts are the part indicated by 203(3) connected to
the second electrode 203 and a part of the first electrode 201
which can be in contact with the outside air (a part of the first
electrode drawn to the outside)].
As a sealing material for forming such a sealing material layer 3,
any conventionally known suitable material may be used in
consideration of adhesiveness, heat resistance, and barrier
properties against moisture, oxygen, and the like, and thereby the
sealing material layer 3 can be formed as needed. For example, it
is possible to use any material, as needed, such as not only epoxy
resins, silicone resins, acrylic resins, methacrylic resins, and so
on, but also the same materials as those cited as the adhesives
usable for forming the above-mentioned adhesive layer. Here, a
sheet-shaped sealing material may be also used to form such a
sealing material layer 3. Such a sheet-shaped sealing material may
be formed by a publicly-known appropriate shape-forming method.
Then, the thickness (t) of the sealing material layer 3 just has to
be a thickness that allows the sealing material layer 3 to cover
the light emitting element 2 such that the light emitting element 2
can be sealed (the thickness just has to have a value larger than
that of the height of the light emitting element 2 from the surface
of the transparent support substrate 1). Thus, the thickness (t) is
not particularly limited, but is preferably 5 to 120 .mu.m, more
preferably 5 to 60 .mu.m, even more preferably 10 to 60 .mu.m, and
most preferably 10 to 40 .mu.m. If the thickness t of the sealing
material layer (the distance between the transparent support
substrate 1 and the sealing substrate 4) is smaller than the above
lower limit, the second electrode 203 and the sealing substrate 4
tend to easily come into contact with each other when being bent,
so that satisfactory inhibition of a short circuit cannot be
achieved and the light-emission performance is also more likely to
degrade. Also in this case, when being bent, the second electrode
203 is pressed with the application of pressure by the asperities
on the surface of the sealing substrate 4, and thereby tends to
come into contact with the first electrode 201 and cause a short
circuit. On the other hand, if the thickness t exceeds the above
upper limit, the surfaces of the sealing material layer in contact
with the outside air increase so much that a large amount of water
vapor may permeate in lateral directions of the sealing material
layer (directions perpendicular to the thickness direction:
directions parallel to the surface of the transparent support
substrate 1). Accordingly, the storage life of the organic EL
device tends to be shortened. A method for disposing such a sealing
material layer 3 to seal the light emitting element 2 will be
described later.
[Sealing Substrate 4]
The sealing substrate 4 is disposed on the sealing material layer
3. Since the sealing material layer 3 is disposed to cover the
light emitting element 2, the light emitting element 2 and the
sealing material layer 3 are present between the light emitting
element 2 and the sealing substrate 4. Thus, the sealing substrate
4 is disposed on the sealing material layer 3 such that the light
emitting element 2 and the sealing material layer 3 are interposed
between the transparent support substrate 1 and the sealing
substrate 4. Such a sealing substrate 4 is used for the purpose of
more efficiently inhibiting water vapor, oxygen and the like from
permeating the inside of the light emitting element 2 from the
surface of the sealing material layer 3 (the surface in contact
with the sealing substrate 4) opposite to the surface of the
sealing material layer 3 in contact with the transparent support
substrate 1, and for the purpose of improving heat dissipation.
Such a sealing substrate 4 is set for use based on the arithmetic
average of roughness profile Ra of JIS B 0601-1994 such that the
surface roughness of a surface S1 of the sealing substrate 4 beside
the sealing material layer 3 has a smaller value than the surface
roughness of the other surface S2 (the surface roughness of the
outer side) of the sealing substrate concerned. If the arithmetic
average of roughness profile Ra of the surface S1 of the sealing
substrate 4 has a larger value than the arithmetic average of
roughness profile Ra of the other surface S2 of the sealing
substrate, the organic EL device is more likely to cause a short
circuit when being bent, because the asperity shape on the surface
S1 of the sealing substrate 4 (a shape of asperities present due to
the roughness of the surface) makes damage such as on the light
emitting element. For this reason, the sealing substrate 4 is used
after being formed such that the arithmetic average of roughness
profile Ra of the surface S1 of the sealing substrate 4 beside the
sealing material layer 3 has a smaller value than the arithmetic
average of roughness profile Ra of the other surface S2 of the
sealing substrate concerned. Note that although it is also
conceivable to perform a treatment of smoothing the surface
roughness of the sealing substrate 4, such a smoothing treatment
(for example, polishing, surface treatment, or the like), if
carried out, incurs a cost increase and a reduction in the economy
in production of the organic EL device to make the mass production
difficult. In addition, if the surface is smoothened too much, the
sealing substrate 4 is more likely to peel off due to a reduction
in the adhesion to the sealing material layer 3, and thereby makes
the organic EL device difficult to use over a long term. Moreover,
when the surface of the sealing substrate 4 is smoothened, the
thermalemissivity tends to be lowered to make heat dissipation
difficult. In the present invention, the smoothing treatment on the
surface of the sealing substrate 4 does not necessary have to be
carried out. Hence, the productivity of the organic EL device can
also be enhanced to a sufficiently high level.
In addition, in the present invention, the arithmetic average of
roughness profile of the surface S1 of the sealing substrate 4
beside the sealing material layer 3 and the thickness of the
sealing material layer 3 need to satisfy a requirement specified by
the following formula (I): 0.002<(Ra/t)<0.2 (I) [in the
formula (I), Ra denotes the arithmetic average of roughness profile
of JIS B 0601-1994 of the surface of the sealing substrate beside
the sealing material layer, and t denotes the thickness of the
sealing material layer]. If the ratio (Ra/t) of the arithmetic
average of roughness profile Ra to the thickness t of the sealing
material layer 3 is 0.002 or less, the surface of the sealing
substrate 4 beside the sealing material layer 3 is so smooth that
the adhesion to the sealing material layer 3 is too low. As a
result, the sealing substrate 4 is more likely to peel off and
moisture is more likely to permeate from the interface between the
sealing material layer 3 and the surface of the sealing substrate 4
beside the sealing material layer 3 to accelerate a deterioration
of the organic EL device. In addition, since the thickness of
sealing material layer 3 tends to be large, moisture is likely to
permeate from portions, exposed to the outside, at the ends of the
sealing material layer 3 to accelerate a deterioration of the
organic EL device. On the other hand, if the ratio (Ra/t) is 0.2 or
more, asperities on the surface of the sealing substrate 4 beside
the sealing material layer 3 are enlarged, whereas the thickness of
the sealing material layer 3 is reduced relatively. In this case,
when being bent, the second electrode 203 and the sealing substrate
4 may come into contact with each other so easily that a short
circuit cannot be satisfactorily inhibited and the light-emission
performance tends to degrade more easily. In addition, when the
organic EL device is bent, the organic EL device tends to be
pressed with application of pressure by the asperities on the
surface of the sealing substrate 4, and resultantly come into
contact with the first electrode 201 to cause a short circuit.
Moreover, since higher effects can be obtained from the same
viewpoints, the ratio (Ra/t) of the arithmetic average of roughness
profile Ra of the surface S1 of the sealing substrate 4 of a side
of the sealing material layer 3 to the thickness t of the sealing
material layer 3 is preferably in a range of 0.003 to 0.03, and
more preferably in a range of 0.005 to 0.01. Note that the
thickness t of the sealing material layer 3 is a thickness measured
from the surface of the transparent support substrate 1, and has
the same value as the distance between the transparent support
substrate 1 and the sealing substrate 4.
The arithmetic average of roughness profile Ra of the surface S1 of
the sealing substrate 4 beside the sealing material layer 3 is
preferably 0.1 to 1.0 .mu.m and more preferably 0.2 to 0.5 .mu.m.
If the surface S1 has an arithmetic average of roughness profile Ra
less than the above lower limit, the surface S1 tends to
deteriorate not only in the adhesion to the sealing agent layer 3
but also in the heat dissipation performance. On the other hand, if
the surface S1 has an arithmetic average of roughness profile Ra
exceeding the above upper limit, the peaks of the asperities on the
surface pierce through the sealing material layer when the organic
EL device is being bent, with the results that the device is likely
to cause a short circuit and the sealing base material 4 and the
second electrode 203 are likely to come into contact with each
other to cause a short circuit. Moreover, in the case where a
device has a structure in which the sealing substrate 4 can be seen
through the transparent support substrate 1, the device tends to
appear slightly dull due to light reflection. In contrast, if the
arithmetic average of roughness profile Ra is the above upper limit
or less, the device having the structure in which the sealing
substrate 4 can be seen through the transparent support substrate 1
tends to improve in design beautifulness because the surface
roughness of the surface S1 of the sealing substrate which can be
seen through the transparent support substrate 1 is constituted by
relatively small surfaces.
The arithmetic average of roughness profile Ra of the outer surface
S2 of the sealing substrate 4 is preferably 0.25 to 3.8 .mu.m, and
is more preferably 0.5 to 2.5 .mu.m. If the arithmetic average of
roughness profile Ra of the surface S2 is less than the above lower
limit, the surface area of the surface S2 becomes smaller and heat
generated in the light emitting element can be dissipated only in a
smaller amount to the outside. As a result, the organic EL device
tends to have a high temperature and thus be promoted to
deteriorate. In addition, in the case where a heat dissipation
layer or heat transmission layer is formed over the surface of the
outer surface S2, the adhesion at the interface between the surface
S2 and the heat dissipation layer or heat transmission layer tends
to decrease to cause peeling-off readily, and thereby the device
tends to be broken easily. On the other hand, if the arithmetic
average of roughness profile Ra of the surface S2 is set to exceed
the above upper limit, the surface S2 needs to be processed further
in a special roughening step, and the productivity tends to
decrease.
Incidentally, to measure the arithmetic average of roughness
profile (the arithmetic average of roughness profile defined by JIS
B 0601 (1994)), a contact-type step and surface roughness measuring
device, for example, may be employed as a measuring device, and the
measurement may be conducted.
Moreover, the ten point height of roughness profile Rz of JIS B
0601-1994 of the surface S1 of the sealing substrate 4 beside the
sealing material layer 3 is preferably 0.4 to 4.0 .mu.m, and more
preferably 0.8 to 2.0 .mu.m. When the ten point height of roughness
profile Rz is less than the above lower limit, the adhesion to the
sealing material layer 3 tends to decrease. On the other hand, when
the ten point height of roughness profile Rz exceeds the above
upper limit, the peaks of the asperities on the surface pierce
through the sealing material layer when the organic EL device is
being bent, with the results that the organic EL device is likely
to cause a short circuit and the sealing substrate 4 and the second
electrode 203 are likely to come into contact with each other to
cause a short circuit.
In the present invention, the ten point height of roughness profile
Rz of JIS B 0601-1994 of the surface (outer surface) S2 of the
sealing substrate 4 is preferably 1.0 to 15 .mu.m, and more
preferably 2 to 10 .mu.m. When the ten point height of roughness
profile Rz is less than the above lower limit, the surface area of
the surface S2 becomes smaller and heat generated in the light
emitting element can be dissipated only in a smaller amount to the
outside. As a result, the organic EL element tends to have a high
temperature and thus be promoted to deteriorate. In addition, in
the case where a heat dissipation layer or heat transmission layer
is formed over the surface of the surface S2, the adhesion at the
interface between the surface S and the heat dissipation layer or
heat transmission layer tends to decrease to cause peeling-off
readily, and thereby the device is more likely to be broken. On the
other hand, if the ten point height of roughness profile Rz of the
outer surface S2 is set to exceed the above upper limit, the
surface S2 needs to be processed further in a special roughening
step, and the productivity tends to decrease.
Incidentally, to measure the ten point height of roughness profile
(the ten point height of roughness profile defined by JIS B 0601
(1994)), a contact-type step and surface roughness measuring
device, for example, may be employed as a measuring device, and the
measurement may be conducted.
A material for such a sealing substrate is not particularly
limited, but is preferably any of metal materials including copper,
copper alloys, aluminum, and aluminum alloys from the viewpoints of
heat dissipation and ease of processing. Examples of the sealing
substrates made of such metal materials include an aluminum foil, a
copper foil, and the like.
Moreover, among such sealing substrates 4, a copper foil produced
by an electrolytic process is more preferably, because the copper
foil produced by the electrolytic process tends to have less
pinholes and produce higher effects in prevention of permeation of
water vapor, oxygen, and so on. In other words, use of such a
copper foil produced by the electrolytic process as the sealing
substrate 4 makes it possible to seal the organic EL more
efficiently, so that a deterioration of the organic EL device due
to permeation of moisture from the pinholes of the copper foil can
be more satisfactorily inhibited. Note that such an electrolytic
process is not particularly limited, but any publicly-known
electrolytic process capable of producing a copper foil may be
employed as needed.
In addition, the thickness of the sealing substrate 4 is not
particularly limited, but is preferably 5 to 100 .mu.m, and more
preferably 8 to 50 .mu.m. When the thickness of the sealing
substrate 4 is less than the above lower limit, it is difficult to
satisfactorily inhibit generation of pinholes in the sealing
substrate 4 during production thereof, and a deterioration of the
organic EL device due to permeation of moisture from the pinholes
tends to be difficult to inhibit at a high level (the sealing
performance tends to be decreased due to the pinholes). On the
other hand, when the thickness of the sealing substrate 4 exceeds
the above upper limit, the flexibility of the sealing substrate 4
is lowered with the result that the curvature radius of the bent
organic EL device in which the sealing substrate 4 is bonded
becomes large. Thus, the flexibility of the organic EL device tends
to be lowered.
In addition, a method for disposing the sealing material layer 3
and the sealing substrate 4 on the transparent support substrate 1
is not particularly limited, and any publicly-known method may be
employed as needed. For example, it is possible to employ a method
for stacking (disposing) the sealing material layer 3 and the
sealing substrate 4 on the transparent support substrate 1, in
which a sealing material made of an adhesive material is applied to
cover the light emitting element 2 on the transparent support
substrate 1; the sealing substrate 4 is stacked thereon; and then
the sealing material is cured and fixed. Instead, it is also
possible to employ a method for stacking (disposing) the sealing
material layer 3 and the sealing substrate 4 on the transparent
support substrate 1, in which a layer made of a sealing material is
formed on the sealing substrate 4 in advance, and then the sealing
substrate 4 on which the layer made of the sealing material is
formed is pressed against the light emitting element 2 such that
the area around the light emitting element 2 can be covered with
the layer made of the sealing material.
Then, the distance between the sealing substrate 4 and the light
emitting element 2 in the thickness direction (the direction
perpendicular to the sealing substrate 4) (the thickness of the
sealing material layer 3 between the light emitting element 2 and
the sealing substrate 4: the distance between the surface S1 of the
sealing substrate 4 and the surface of the second electrode 203 in
contact with the sealing agent layer 3) is preferably 5 to 120
.mu.m, and more preferably 10 to 60 .mu.m. If the distance between
the sealing substrate 4 and the light emitting element 2 (the
thickness of the sealing material layer 3 between the light
emitting element 2 and the sealing substrate 4) is less than the
above lower limit, the second electrode 203 and the sealing
substrate 4 cannot be always satisfactorily inhibited from coming
into contact with each other when being bent, so that it tends to
be difficult to satisfactorily inhibit a short circuit and the
light-emission performance tends to degrade easily. Also, when
being bent, the second electrode 203 is pressed with the
application of pressure by the asperities on the surface of the
sealing substrate 4, and thereby tends to come into contact with
the first electrode 201 and cause a short circuit. On the other
hand, if the distance between the sealing substrate 4 and the light
emitting element 2 exceeds the above upper limit, the surfaces of
the sealing material layer in contact with the outside air increase
so much that a larger amount of water vapor may permeate in the
lateral directions of the sealing material layer (the directions
perpendicular to the thickness direction: the directions parallel
to the surface of the transparent support substrate 1).
Accordingly, shortening of the storage life of the organic EL
device tends to be difficult to inhibit at a higher level.
Heretofore, the preferred embodiment of the organic
electroluminescent device of the present invention has been
described with reference to FIGS. 1 and 2. However, the organic
electroluminescent device of the present invention should not be
limited to the above embodiment.
For example, the light emitting element 2 includes the pair of
electrodes (the first electrode 201 and the second electrode 203),
and the luminescent layer 202 disposed between the electrodes in
the embodiment illustrated in FIG. 1. In the organic
electroluminescent device in the present invention, however, the
light emitting element 2 may include other layers as needed, as
long as the object and the effects of the present invention are not
impaired. Hereinafter, description will be provided for such other
layers.
As such other layers which are usable in the organic EL device in
addition to the pair of electrodes (the first electrode 201 and the
second electrode 203) and the luminescent layer 202, it is possible
to employ, as needed, any publicly-known layers used in the organic
EL device, for example, a layer disposed between the cathode and
the luminescent layer, and a layer disposed between the anode and
the luminescent layer. As the layer disposed between the cathode
and the luminescent layer, there are an electron injection layer,
an electron transport layer, a hole blocking layer, and so on.
Here, when only a single layer is provided between the cathode and
the luminescent layer, the layer is an electron injection layer.
Then, when two or more layers are provided between the cathode and
the luminescent layer, the layer in contact with the cathode is
called an electron injection layer and the other layer(s) is called
an electron transport layer.
The electron injection layer is a layer having a function to
improve the efficiency of electron injection from the cathode. The
electron transport layer is a layer having a function to improve
electron injection from the electron injection layer or from
another electron transport layer closer to the cathode. Here, if
the electron injection layer or the electron transport layer has a
function to block the transport of holes, this layer is also called
a hole blocking layer in some cases. Whether or not a layer has the
function to block the transport of holes as described above can be
checked by fabricating, for example, an element which allows only a
hole current to flow, and by confirming the effect of blocking with
a decrease in the current value.
As the layer provided between the anode and the luminescent layer,
there are so-called a hole injection layer, a hole transport layer,
an electron blocking layer, and so on. Here, when only a single
layer is provided between the anode and the luminescent layer, the
layer is a hole injection layer. Then, when two or more layers are
provided between the anode and the luminescent layer, the layer in
contact with the anode is called a hole injection layer and the
other layer(s) is called a hole transport layer or the like. The
hole injection layer is a layer having a function to improve the
efficiency of hole injection from the cathode. The hole transport
layer is a layer having a function to improve hole injection from
the hole injection layer or from another hole transport layer
closer to the anode. Note that if the hole injection layer or the
hole transport layer has a function to block the transport of
electrons, this layer is called an electron blocking layer in some
cases. Whether or not a layer has the function to block the
transport of electrons can be checked by fabricating, for example,
an element which allows only an electron current to flow, and by
confirming the effect of blocking with a decrease in the current
value.
As a structure of the light emitting element including such other
layers, there area structure in which an electron transport layer
is provided between the cathode and the luminescent layer, a
structure in which a hole transport layer is provided between the
anode and the luminescent layer, a structure in which an electron
transport layer is provided between the cathode and the luminescent
layer and a hole transport layer is provided between the anode and
the luminescent layer, and so on. As examples of the structures of
the embodiment illustrated in FIG. 1 and other light emitting
elements, the following structures a) to d) are presented: a)
anode/luminescent layer/cathode (the embodiment illustrated in FIG.
1); b) anode/hole transport layer/luminescent layer/cathode; c)
anode/luminescent layer/electron transport layer/cathode; and d)
anode/hole transport layer/luminescent layer/electron transport
layer/cathode. (Here, / indicates that layers on both sides are
layered next to each other. The same applies below.)
Here, the hole transport layer is a layer having a function to
transport holes, and the electron transport layer is a layer having
a function to transport electrons. In the following description,
the electron transport layer and the hole transport layer are
referred to as a general name, that is, a charge transport layer.
In addition, two or more layers may be provided as each of the
luminescent layer, the hole transport layer, and the electron
transport layer, independently. Moreover, among charge transport
layers provided next to an electrode, a layer having a function to
improve charge injection from the electrode and producing an effect
of reducing a drive voltage of the device is generally called a
charge injection layer (a hole injection layer or an electron
injection layer) in particular.
Moreover, the aforementioned charge injection layer or an
insulating layer having a film thickness of 2 nm or smaller may be
provided next to an electrode in order to enhance the adhesion to
the electrode or to improve charge injection from the electrode. In
addition, a thin buffer layer may be inserted into the interface
with any of the charge transport layer and the luminescent layer in
order to enhance the adhesion at the interface, prevent mixing, and
do the like. Thus, by taking account of the light emission
efficiency and the device life, it is possible to design the number
and the order of layers layered in the light emitting element and
the thickness of each layer as needed and to use the layers.
As a light emitting element (organic EL element) provided with such
a charge injection layer (electron injection layer and/or hole
injection layer), there are one having a structure in which a
charge injection layer is provided next to the cathode, one having
a structure in which a charge injection layer is provided next to
the anode, and so on.
As examples of the structures of such light emitting elements
(organic EL elements), the following structures e) to p) are
presented: e) anode/charge injection layer/luminescent
layer/cathode; f) anode/luminescent layer/charge injection
layer/cathode; g) anode/charge injection layer/luminescent
layer/charge injection layer/cathode; h) anode/charge injection
layer/hole transport layer/luminescent layer/cathode; i) anode/hole
transport layer/luminescent layer/charge injection layer/cathode;
j) anode/charge injection layer/hole transport layer/luminescent
layer/charge injection layer/cathode; k) anode/charge injection
layer/luminescent layer/charge transport layer/cathode; l)
anode/luminescent layer/electron transport layer/charge injection
layer/cathode; m) anode/charge injection layer/luminescent
layer/electron transport layer/charge injection layer/cathode; n)
anode/charge injection layer/hole transport layer/luminescent
layer/charge transport layer/cathode; o) anode/hole transport
layer/luminescent layer/electron transport layer/charge injection
layer/cathode; and p) anode/charge injection layer/hole transport
layer/luminescent layer/electron transport layer/charge injection
layer/cathode.
Note that, in the case of forming a multilayer body including a
luminescent layer and another layer (for example, a charge
transport layer to be described later, or the like), it is
desirable to forma hole transport layer on the anode before the
luminescent layer is provided, or to form an electron transport
layer after the luminescent layer is provided. Moreover, materials
for these other layers are not particularly limited, and any
publicly-known materials may be used as needed. A production method
thereof is also not particularly limited, and any publicly-known
method may be used as needed. For example, as a hole transporting
material for forming a hole transport layer, which is a layer
provided between the anode and the luminescent layer or the hole
injection layer and the luminescent layer, there are: heterocyclic
compounds typified by triphenyl amines, bis compounds, pyrazoline
derivatives, and porphyrin derivatives; and polymer compounds such
as polycarbonates having any of the above monomers at the side
chains, styrene derivatives, polyvinyl carbazoles, and polysilanes.
Then, the film thickness of the hole transport layer is preferably
about 1 nm to 1 .mu.m.
Moreover, as a material for forming a hole injection layer (a layer
that can be provided between the anode and the hole transport layer
or between the anode and the luminescent layer) among the
aforementioned charge injection layers, there are phenylamine-based
compounds, starburst amine-based compounds, phthalocyanine-based
compounds, oxides such as vanadium oxide, molybdenum oxide,
ruthenium oxide, and aluminum oxide, amorphous carbons,
polyanilines, polythiophene derivatives, and so on.
In addition, as a material for forming the electron transport
layer, which is a layer that can be provided between the
luminescent layer and the cathode or between the luminescent layer
and the electron injection layer, there are, for example,
substances, such as oxadiazoles and aluminum quinolinol complexes,
which generally form stable radical anions and have high ionization
potential. Specifically, there are 1,3,4-oxadiazole derivatives,
1,2,4-triazole derivatives, imidazole derivatives, and so on. The
film thickness of the electron transport layer is preferably about
1 nm to 1 .mu.m.
Further, as the electron injection layer (a layer that can be
provided between the electron transport layer and the cathode or
between the luminescent layer and the cathode) among the charge
injection layers, it is possible to provide, depending on a kind of
the luminescent layer, for example, an electron injection layer
having a monolayer structure of a Ca layer, or an electron
injection layer having a multilayer structure including a Ca layer
and a layer made of any one or two of metals included in Groups IA
and IIA of the periodic table excluding Ca and each having a work
function of 1.5 to 3.0 eV, and oxides, halides, and carbonates of
these metals. Examples of the metals included in Group IA of the
periodic table and each having a work function of 1.5 to 3.0 eV,
and their oxides, halides, and carbonates are lithium, lithium
fluoride, sodium oxide, lithium oxide, lithium carbonate, and so
on. Meanwhile, examples of the metals included in Group IIA of the
periodic table excluding Ca and each having a work function of 1.5
to 3.0 eV, and their oxides, halides, and carbonates are strontium,
magnesium oxide, magnesium fluoride, strontium fluoride, barium
fluoride, strontium oxide, magnesium carbonate, and so on. The
electron injection layer is formed by a vapor deposition method, a
sputtering method, a printing method, or the like. The film
thickness of the electron injection layer is preferably about 1 nm
to 1 .mu.m.
In the foregoing preferred embodiment of the organic
electroluminescent device of the present invention, the gas-barrier
multilayer film is described with reference to FIG. 2 as a
preferred example of the transparent support substrate 1 used in
the device. However, the structure of the gas-barrier multilayer
film is also not limited to that in the embodiment illustrated in
FIG. 2, and may further include a thin film layer or have another
multilayer structure. Here, as an example of a gas-barrier
multilayer film further including a thin film layer, there is a
gas-barrier multilayer film having a structure in which "first thin
film layer/first base material layer/adhesive layer/second thin
film layer/second base material layer/third thin film layer" are
layered in this order (here, "/" indicates that these layers are
layered next to each other) or the like. Such a gas-barrier
multilayer film having the structure in which the "first thin film
layer/first base material layer/adhesive layer/second thin film
layer/second base material layer/third thin film layer" are layered
in this order may be produced as needed, for example, by employing
the same method as the foregoing method including steps (A) and
(B), except that a film member in which thin film layers are formed
on both surfaces of a base material is prepared as a second film
member in the aforementioned step (A) and is used.
EXAMPLES
Hereinafter, the present invention will be described in more
details based on Examples and Comparative Examples, but the present
invention should not be limited to the following Examples.
Preparation Example 1
<Preparation of Film Member (A)>
Using the same method as the method described in Example 1 of JP
2011-73430 A except that the degree of vacuum in the vacuum chamber
was changed to 1 Pa, thin film deposition by the plasma CVD method
was carried out on a base material made of a biaxially oriented
polyethylene naphthalate film (PEN film, thickness: 100 .mu.m,
width: 350 mm, trade name "Teonex Q65FA" manufactured by Teij in
DuPont Films Japan Limited) to obtain a multilayer film including
the base material on which a thin film layer having a thickness of
1.2 .mu.m was formed (a multilayer body in which the thin film
layer/base material layer are layered in this order: hereinafter
referred to as "film member (A)").
<Preparation of Film Member (B)>
After the film member (A) was obtained as described above, the film
member (A) was used in place of the base material, and a new thin
film was formed on the surface of the film member (A), on which the
thin film layer was not formed, under the same conditions as the
deposition conditions employed in the preparation of the film
member (A) to obtain a multilayer film including the base material
on both surfaces of which the thin film layers having a thickness
of 1.2 .mu.m were formed (a multilayer body in which the thin film
layer/base material layer/thin film layer are layered in this
order: hereinafter referred to as "film member (B)").
Here, the thin film layers formed in the film members (A) and (B)
were subjected to XPS depth profile measurement under the following
conditions to obtain silicon distribution curves, oxygen
distribution curves, carbon distribution curves and oxygen carbon
distribution curves. Then, the carbon distribution curve of each
thin film layer was confirmed to have at least one distinct
extremum, and have an absolute value of the difference between the
maximum value and the minimum value of the atomic ratio of carbon
being 5 at % or greater, and the atomic ratio of silicon, the
atomic ratio of oxygen, and the atomic ratio of carbon were
configured to satisfy a requirement represented by the following
formula (1): (atomic ratio of oxygen)>(atomic ratio of
silicon)>(atomic ratio of carbon) (1). <XPS Depth Profile
Measurement Conditions> Etching ion species: Argon (Ar+);
Etching rate (a value in terms of SiO.sub.2 thermal oxide film):
0.05 nm/sec; Etching interval (a value in terms of SiO.sub.2): 10
nm; X-ray Photoelectron Spectroscope: manufactured by Thermo Fisher
Scientific K.K., model name "VG Theta Probe"; X-ray for
irradiation: single crystal spectral AlK.alpha.; and X-ray spot and
its size: an oval shape of 800.times.400 .mu.m.
Further, a gas barrier property of the film member (A) was measured
by a method in accordance with a calcium corrosion method (a method
described in JP 2005-283561 A). Specifically, metal calcium was
deposited on the film member after a drying treatment, and then was
sealed with metal aluminum from above. After that, the resultant
film member was fixed to a glass plate, and then was sealed with
resin to obtain a sample. Under the conditions of a temperature of
40.degree. C. and a humidity of 90% RH, the water vapor
permeability of the sample was calculated by image analysis
examining an increase of corrosion points over time. Here, in
calculating the water vapor permeability as mentioned above, images
of the corrosion points were captured with a microscope, and then
was taken into a personal computer. Then, each of the images of the
corrosion points was binarized and the water vapor permeability was
calculated by calculating and obtaining the corrosion area. As a
result, the water vapor permeability of the film member (the base
material on the surface of which the thin film layer was formed)
was 1.times.10.sup.-5 g/m.sup.2/day. Note that, using a sample made
only of the base material (PEN film), the gas barrier property was
also measured in the same way using the above method in accordance
with the calcium corrosion method (the method described in JP
2005-283561 A), and the gas barrier property of the base material
was found to be 1.3 g/m.sup.2/day. Based on these result, it was
confirmed that the "water vapor permeability of base material with
thin film layer formed" takes a value smaller by two or more digits
than a value of the "water vapor permeability of base material".
These results revealed that the thin film layers in the film
members (A) and (B) each have gas barrier properties.
<Preparation of Gas-Barrier Multilayer Film>
The film member (A) and the film member (B) obtained as described
above were both dried in a vacuum oven at a temperature condition
of 100.degree. C. for 360 minutes. Thereafter, the two film members
were taken out from the vacuum oven to the atmospheric air
(temperature: 25.degree. C., relative humidity: 50%, humidity
ratio: 10 g/kg (dry air)). Then, by a bonding apparatus with a
silicone rubber roll having a rubber hardness of 60, the film
member (A) and the film member (B) were bonded together with an
adhesive such that the surface of the film member (A) on the base
material side faces the thin film layer of the film member (B) to
obtain a gas-barrier multilayer film. The adhesive used herein is a
two-part epoxy adhesive which is cured at room temperature
(25.degree. C.) when a base resin composed of a base resin composed
of a bisphenol A epoxy resin and a curing agent composed of a
modified polyamide are mixed. Here, a time required to start the
step of bonding the two film members after taking out the two film
members from the vacuum oven was 10 minutes and a time required for
the bonding was 15 minutes. Thus, it took 25 minutes in total to
form the gas-barrier multilayer film after the two film members
after the drying step were taken out from the vacuum oven. The
multilayer structure of the gas-barrier multilayer film thus
obtained is a structure in which the "first thin film layer/first
base material layer/adhesive layer/second thin film layer/second
base material layer/third thin film layer" are layered in this
order. Note that, in the gas-barrier multilayer film, a multilayer
structure portion of the "first thin film layer/first base material
layer" is a structure derived from the film member (A), and a
multilayer structure portion of the "second thin film layer/second
base material layer/third thin film layer" is a structure derived
from the film member (B). In addition, the hygroscopicity (the
aforementioned ratio of moisture absorption Bn) of the gas-barrier
multilayer film thus obtained was measured as described above, and
the gas-barrier multilayer film was found to be capable of
absorbing and retaining water in a weight of 0.29% by mass of its
own weight.
Example 1
On the first thin film layer (the thin film layer derived from the
film member (A)) in the gas-barrier multilayer film obtained in
Preparation Example 1, an ITO film with a film thickness of 150 nm
was deposited in patterns by a sputtering method using a metal
shadow mask. By this pattern deposition, the ITO film was deposited
in such patterns as to form two regions on the surface of the
gas-barrier multilayer film, and one of the regions was used as a
lead electrode for the cathode, whereas the other region was used
as the anode (ITO electrode).
Next, the surface of the gas-barrier multilayer film on which the
ITO film (ITO electrode) was formed was subjected to a UV-O.sub.3
treatment for 15 minutes using a UV-O.sub.3 apparatus (manufactured
by TECHNOVISION, INC.), so that the surface on which the ITO film
was formed was cleaned and modified.
Subsequently, a filtrate obtained by filtering a suspension of
poly(3,4)ethylenedioxythiophene/polystyrenesulfonic acid (trade
name "AI4083" produced by Heraeus K. K.) through a 0.2 micron
filter was spin-coated to form a film on the surface of the
gas-barrier multilayer film on which the ITO film was formed,
followed by drying on a hot plate at a temperature condition of
130.degree. C. for 30 minutes in the atmospheric air. Thus, a hole
injection layer with a thickness of 65 nm was formed on the ITO
film.
Next, a xylene solution in which a luminescent material (polymer
compound 1) was dissolved in xylene as an organic solvent was
prepared. Note that such a luminescent material (polymer compound
1) was prepared in the same method as the method for preparing the
composition described in Example 1 of JP 2012-144722 A. The
concentration of the polymer compound 1 in the xylene solution was
set to 1.2% by mass.
Next, the xylene solution was applied by spin-coating in the
atmospheric air onto the surface, on which the hole injection layer
was formed, of the gas-barrier multilayer film on which the ITO
film and the hole injection layer were formed, and thereby a
coating film having a thickness of 80 nm for a luminescent layer
was formed. Thereafter, the resultant gas-barrier multilayer film
was allowed to stand and was dried under a temperature condition of
130.degree. C. for 10 minutes in a nitrogen gas atmosphere in which
the oxygen concentration and the moisture concentration were each
controlled at a volume ratio of 10 ppm or less, and thereby the
luminescent layer was stacked on the hole injecting layer.
Subsequently, the hole injection layer and the luminescent layer
formed on contact parts to be in contact with external electrodes
(the parts of the lead electrodes for the anode and the cathode)
were removed, and thereby these parts were exposed to become
capable of coming into contact with the external electrodes. After
that, the gas-barrier multilayer film on which the ITO film, the
hole injection layer, and the luminescent layer were formed was
transferred to a vapor deposition chamber, and was aligned in
position with a cathode mask. Then, vapor deposition of a cathode
was carried out by rotating the mask and a base board to deposit
the cathode such that the cathode was stacked on the surface of the
luminescent layer and was electrically connected to the part
constituting the lead electrode for the cathode. The cathode thus
formed has a multilayer structure in which sodium fluoride (NaF)
was firstly heated and vapor-deposited in a thickness of 4 nm at a
vapor deposition rate of about 0.5 .ANG./sec, and then aluminum
(Al) was vapor-deposited in a thickness of 100 nm at a vapor
deposition rate of about 4 .ANG./sec.
Next, a copper foil with a thickness of 35 .mu.m was cut by a
roller cutter to prepare a sealing substrate. Specifically, the
copper foil used herein had surface roughness with an arithmetic
average of roughness profile Ra of 0.25 .mu.m and a ten point
height of roughness profile Rz of 1 .mu.m on one surface (simply
referred to as the "first surface" for convenience in some cases
below), and had surface roughness with an arithmetic average of
roughness profile Ra of 2.4 .mu.m and a ten point height of
roughness profile Rz of 9.5 .mu.m on the other surface (simply
referred to as the "second surface" for convenience in some cases
below). The copper foil was cut herein into a shape in such a size
that a cut piece of the copper foil, when viewed from the cathode
side after being stacked on the cathode side, can entirely hide the
cathode and the luminescent layer while party exposing the contact
parts (the parts constituting the lead electrodes for the anode and
the cathode) with the external electrodes to the outside (as
illustrated in FIG. 3, a shape in such a size that, when viewed
from above, an electrolytic copper foil (sealing substrate 4) has
an area larger than the cathode so that the cathode cannot be
viewed, and the contact parts on the gas-barrier multilayer film
formed for contact with the outside (the parts constituting the
lead electrodes for the anode and the cathode) partly stick out of
the foil and thus can be viewed). Here, the copper foil thus
prepared had a length of 40 mm, a width of 40 mm, and a thickness
of 35 .mu.m. Moreover, an electrolytic copper foil produced by an
electrolytic process was used as the copper foil.
In addition, a two-part epoxy adhesive which is cured at room
temperature (25.degree. C.) when a base resin composed of a
bisphenol A epoxy resin and a curing agent composed of a modified
polyamide are mixed was prepared as a sealing material. Then, the
sealing substrate (the foregoing copper foil) was heated at a
temperature condition of 130.degree. C. for 15 minutes in a
nitrogen atmosphere to remove water adsorbed on the surfaces of the
sealing substrate (subjected to a drying treatment).
Next, sealing was carried out in such a way that the sealing
material was applied to cover the light emitting unit constituted
by a multilayer structure portion including the ITO film/hole
injection layer/luminescent layer/cathode, and then the sealing
substrate was bonded to a layer of the sealing material such that
the sealing substrate faces the luminescent layer. Specifically,
the sealing material (adhesive) was applied to cover the multilayer
structure portion including the ITO film/hole injection
layer/luminescent layer/cathode (but excluding portions of the
connecting parts (the parts constituting the lead electrodes) for
allowing the electrodes to be electrically connected to the
outside). Then, in the nitrogen, the sealing substrate was bonded
with the first surface (the surface with a Ra of 0.25 .mu.m) being
in contact, with no air bubbles allowed to enter, with the sealing
material (adhesive) layer on the surface of the gas-barrier
multilayer film after the cathode was formed. In this way, the
light emitting element (the multilayer structure portion including
the ITO film/hole injection layer/luminescent layer/cathode:
excluding portions of the lead electrodes) was sealed to fabricate
the organic EL device. The organic EL device thus fabricated is
flexible, and has a structure in which the hole injection layer is
further stacked in the light emitting element 2 of the organic EL
device in the embodiment illustrated in FIG. 1 (the structure of
the organic EL device is basically the same as that of the light
emitting element 2 illustrated in FIG. 1, but is different in that
the light emitting element further includes the hole injection
layer). Here, as the transparent support substrate 1, the
gas-barrier multilayer film having a structure where the "first
thin film layer/first base material layer/adhesive layer/second
thin film layer/second base material layer/third thin film layer"
were layered in this order was used. In addition, the thickness of
the sealing material layer (the height from the transparent support
substrate) was 10 .mu.m, and the distance between the sealing
substrate (copper foil) and the cathode was 10 .mu.m. FIG. 3
illustrates a schematic view of such an organic EL device when
viewed from the sealing substrate side. As illustrated in FIG. 3,
when the organic EL device obtained in Example 1 is viewed from the
sealing substrate 4 side, it is possible to see the transparent
support substrate 1, the part of the anode 201 sticking out (the
connecting part with the outside: the part constituting the lead
electrode), the connecting part (lead electrode) 203(a) where the
cathode is to be connected to the outside, and the sealing
substrate 4. In this way, in this Example, the sealing with the
sealing material and the sealing substrate was provided so as to
seal and cover the area around the light emitting element (the
multilayer structure portion including the ITO film/hole injection
layer/luminescent layer/cathode) while leaving the parts of the
lead electrodes for the anode and the cathodes connectable to the
outside (see FIGS. 1 and 3). Note that, in this organic EL device,
the arithmetic average of roughness profile of the surface of the
sealing substrate in contact with the sealing material layer had a
smaller value than the arithmetic average of roughness profile of
the surface of the sealing substrate out of contact with the
sealing material layer, and the ratio (Ra/t) of the arithmetic
average of roughness profile Ra of the surface of the sealing
substrate in contact with the sealing material layer to the
thickness t of the sealing material layer was 0.025. In addition,
the gas-barrier multilayer film (transparent support substrate 1)
illustrated in FIG. 3 had a lateral length X of 50 mm, and the
sealing substrate 4 had a lateral length Y of 40 mm. Moreover, in
this Example, a light emission area (the area of a portion from
which light is emitted) in the light emitting element was a length
of 10 mm and a width of 10 mm.
Comparative Example 1
An organic EL device was fabricated in the same way as in Example 1
except that, in the fabrication of the multilayer body for sealing,
the sealing substrate was bonded onto the sealing material layer
such that the surface (second surface) with the arithmetic average
of roughness profile Ra of 2.4 .mu.m was in contact with the
sealing material layer, instead of bonding the sealing substrate
onto the sealing material layer such that the surface (first
surface) with the arithmetic average of roughness profile Ra of
0.25 .mu.m was in contact with the sealing material layer. In this
organic EL device, the arithmetic average of roughness profile of
the surface of the sealing substrate in contact with the sealing
material layer had a larger value than the arithmetic average of
roughness profile of the surface of the sealing substrate out of
contact with the sealing material layer, and the ratio (Ra/t) of
the arithmetic average of roughness profile Ra of the surface of
the sealing substrate in contact with the sealing material layer to
the thickness t of the sealing material layer was 0.24.
[Characteristic Evaluation of Organic EL Devices Obtained in
Example 1 and Comparative Example 1]
After application of a reverse bias voltage, the organic EL
elements obtained in Example 1 and Comparative Example 1 were each
caused to emit light by application of a forward bias voltage.
Then, the current densities of the organic EL elements obtained in
Example 1 and Comparative Example 1 in an initial state (in a state
before a bending test described below) were measured at a reverse
bias voltage of -5 V and determined to be -0.29 mA/cm.sup.2
(Example 1) and -0.29 mA/cm.sup.2 (Comparative Example 1). These
current densities were each determined by measuring a current and a
voltage using a DC power device and a multimeter as a measuring
device.
Next, a step of bending each of the organic EL elements in such a
way as to curve the sides of the organic EL element having the
length X illustrated in FIG. 3 and then restoring the organic EL
element to the original state was repeated 100 times (bending
test). Here, the organic EL elements were each bent to have a
curvature radius of 25 mm when bent at maximum.
Subsequently, after application of a reverse bias voltage, the
organic EL elements after the bending test were each caused to emit
light by application of a forward bias voltage. After that, the
current densities at the reverse bias voltage of -5 V were
measured. As a result, the current densities of the organic EL
elements obtained in Example 1 and Comparative Example 1 after the
bending test were -0.29 mA/cm.sup.2 (Example 1) and -0.4
mA/cm.sup.2 or more (Comparative Example 1).
Thus, the organic EL device obtained in Example 1 was found having
no failure due to a short circuit (short-circuit failure) in
particular, because the current density was -0.29 mA/cm.sup.2 in
the initial state and was -0.29 mA/cm.sup.2 after the bending test
and there was no difference between the current density values
(equal values) before and after the bending test. On the other
hand, the organic EL device obtained in Comparative Example 1 was
found having a failure due to a short circuit (short-circuit
failure) after the bending test, because the current density was
-0.29 mA/cm.sup.2 in the initial state and was -0.4 mA/cm.sup.2 or
more after the bending test and it was confirmed that the bending
test caused the current density to increase by an amount greatly
exceeding a measurement error. In addition, the light emitting
states were examined. As a result, it was found that the organic EL
element obtained in Example 1 had almost the same light emitting
state before and after the bending test, and maintained the
light-emission performance satisfactorily, whereas the organic EL
element obtained in Comparative Example 1 had problems such as
reduction in the emission luminance and generation of dark spots,
and failed to maintain the light-emission performance
satisfactorily due to the bending test.
From these results, it was confirmed that the organic
electroluminescent device (Example 1) of the present invention is
capable of satisfactorily inhibiting the occurrence of a short
circuit after being bent, and is satisfactorily usable in a use
environment in which the device is to be bent repeatedly.
INDUSTRIAL APPLICABILITY
As described above, according to the present invention, it is
possible to provide an organic electroluminescent device capable of
satisfactorily inhibiting the occurrence of a short circuit after
being bent.
Therefore, the organic electroluminescent device of the present
invention is a device that is capable of satisfactorily inhibiting
a failure due to bending and thus is highly reliable in bending,
and therefore is suitably usable in, for example, a flexible
illumination apparatus, a flexible planar light source, a flexible
display, and the like.
REFERENCE SIGNS LIST
1: transparent support substrate 2: light emitting element 3:
sealing material layer 4: sealing substrate 100(a): first base
material layer 100(b): second base material layer 101(a): first
thin film layer having gas barrier properties 101(b): second thin
film layer having gas barrier properties 102: adhesive layer 201:
first electrode 202: luminescent layer 203: second electrode
203(a): lead electrode of second electrode X: lateral length of
transparent support substrate Y: lateral length of sealing
substrate S1 and S2: surfaces of sealing substrate
* * * * *
References